RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
hi, comments in-line: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Howard C. Berkowitz Sent: Wednesday, February 19, 2003 2:17 PM To: [EMAIL PROTECTED] Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] At 6:51 PM + 2/19/03, Vicky Rode wrote: >comments in-line: > > >-Original Message- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of >Howard C. Berkowitz >Sent: Tuesday, February 18, 2003 6:42 AM >To: [EMAIL PROTECTED] >Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > >At 5:30 AM + 2/18/03, Ken Diliberto wrote: >>The nit I'm picking is inline... (I'm feeling like chipping in tonight) >> >>>>> "The Long and Winding Road" >>02/17/03 06:13PM >>> >> >>[snip] >> >>if I have a 75xx router with 300 ethernet ports, and I bridge all >>those >>ports, do I have an L3 switch, or a router? >> >>[KD] >>You have a router performing L2 operations (forwarding, switching, >>bridging -- whatever). Would a cheap Linksys switch be faster? >> >>What makes a L3 switch in my mind is where the forwarding happens. If >>the L3 CPU (new way to look at it?) has to handle every packet, that's a >>router. If the first L3 packet is handled by the CPU which then >>programs ASICs to handle the rest of the flow without bothering the CPU, >>that's an L3 switch. Is there a difference from a packet/network >>perspective? No. The L2 headers and L3 headers are all properly >>updated in both cases (at least we *hope* they are) and traffic is >>delivered most of the time. (If it was delivered all the time, networks >>wouldn't need us to fix them) :-) > >Does that make a 7500 with VIPs a L3 switch? A 12000 with >distributed forwarding processors? >-- >it dependscall it (d)cef switching router if you want but i have to >kinda agree with ken's comments. in my opinion the major difference between >a tradition router and a l3 switch is the way packet switching takes place. >in a tradition router the packet switching are done in software >(microprocessor based), Big difference if the microprocessors (note plural) aren't doing anything except forwarding, and run a real time OS. The key thing is that you don't want forwarding going through the processor that runs routing protocols, system management, etc. -vicky> true enough. but in my opinion it depends on what hw you have in play and for what purpose. whether it is going to be classic line cards, switch fabric cards or distributed forwarding cards and whether the packet switching is going to be flow based or cef based. i guess one should have a good understanding for what their network traffic looks like and a good baseline before retrofitting to high powered hw which can be a big waste of money and resources. A real challenge is where to implement QoS, because it tends to get beyond the complexity of a true ASIC and really has to be done in a microcode-loaded processor. --vicky> for me polling and gathering different qos snmp data variables has been a challenge rather than hw issue, so i can't really comment on that. >whereas in l3 switch it is done by asic in hw and >mls is used to increase routing performance by doing packet switching and >rewrites in hw (asics). There's a bit of Cisco marketing-speak here, which was actually a reaction to competitors who brought up the concept "switch if you can, route when you must." Hardware and software technology have moved on since then, and the line is much more blurred between the two. It's more important to think of separating the forwarding, control, and upper layer services path (and being sure there's no mutual interference) than it is to consider the actual hardware processing elements (ASICs, microcoded or RISC processors, etc.) ---vicky> in my opinion, what's important and necessary is control/forward plane inter-relation. that's all. regards, /vicky This emphasis on ASICs also ignores a couple of common bottlenecks: memory and fabric. To some extent, you can get around memory limitations by having distributed memories for distributed processors. For the fabric, you can move from shared bus, to shared memory, and eventually to crossbar (ignoring optical trends). As I mentioned in a previous post that's partially below, you don't necessarily need ASICs if you have enough distributed processors, using the term "processor" to include microcode sequencers, FPGAs and EA-FPGAs, etc. In research prototypes, I've been involved in routers that had true processors, ru
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
At 6:51 PM + 2/19/03, Vicky Rode wrote: >comments in-line: > > >-Original Message- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of >Howard C. Berkowitz >Sent: Tuesday, February 18, 2003 6:42 AM >To: [EMAIL PROTECTED] >Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > >At 5:30 AM + 2/18/03, Ken Diliberto wrote: >>The nit I'm picking is inline... (I'm feeling like chipping in tonight) >> >>>>> "The Long and Winding Road" >>02/17/03 06:13PM >>> >> >>[snip] >> >>if I have a 75xx router with 300 ethernet ports, and I bridge all >>those >>ports, do I have an L3 switch, or a router? >> >>[KD] >>You have a router performing L2 operations (forwarding, switching, >>bridging -- whatever). Would a cheap Linksys switch be faster? >> >>What makes a L3 switch in my mind is where the forwarding happens. If >>the L3 CPU (new way to look at it?) has to handle every packet, that's a >>router. If the first L3 packet is handled by the CPU which then >>programs ASICs to handle the rest of the flow without bothering the CPU, >>that's an L3 switch. Is there a difference from a packet/network >>perspective? No. The L2 headers and L3 headers are all properly >>updated in both cases (at least we *hope* they are) and traffic is >>delivered most of the time. (If it was delivered all the time, networks >>wouldn't need us to fix them) :-) > >Does that make a 7500 with VIPs a L3 switch? A 12000 with >distributed forwarding processors? >-- >it dependscall it (d)cef switching router if you want but i have to >kinda agree with ken's comments. in my opinion the major difference between >a tradition router and a l3 switch is the way packet switching takes place. >in a tradition router the packet switching are done in software >(microprocessor based), Big difference if the microprocessors (note plural) aren't doing anything except forwarding, and run a real time OS. The key thing is that you don't want forwarding going through the processor that runs routing protocols, system management, etc. A real challenge is where to implement QoS, because it tends to get beyond the complexity of a true ASIC and really has to be done in a microcode-loaded processor. >whereas in l3 switch it is done by asic in hw and >mls is used to increase routing performance by doing packet switching and >rewrites in hw (asics). There's a bit of Cisco marketing-speak here, which was actually a reaction to competitors who brought up the concept "switch if you can, route when you must." Hardware and software technology have moved on since then, and the line is much more blurred between the two. It's more important to think of separating the forwarding, control, and upper layer services path (and being sure there's no mutual interference) than it is to consider the actual hardware processing elements (ASICs, microcoded or RISC processors, etc.) This emphasis on ASICs also ignores a couple of common bottlenecks: memory and fabric. To some extent, you can get around memory limitations by having distributed memories for distributed processors. For the fabric, you can move from shared bus, to shared memory, and eventually to crossbar (ignoring optical trends). As I mentioned in a previous post that's partially below, you don't necessarily need ASICs if you have enough distributed processors, using the term "processor" to include microcode sequencers, FPGAs and EA-FPGAs, etc. In research prototypes, I've been involved in routers that had true processors, running on the forwarding boards, that ran a real-time OS. These processors did have certain functions custom-built in hardware. Also, the processors can have coprocessors -- the Nortel Shasta products, for example, have an encryption chip more or less next to general board-level processors, with a high-speed path between them. Even with ASICs, the L2 and L3 decisions, rewrite, etc. often are in separate chips. Remember a processor can be implemented as bit slices operating in a set of ICs. > > > >Substituting router for L3 switch is a good idea, but go farther than >that. You can think of a high-performance router as a small hidden >network, containing one or more (think high availability) path >determination "routing" processors/hosts that download FIB >information to multiple forwarding processors/hosts. One public and >vendor-independent discussion of this architecture continues in the >IETF FORCES Working Group (go to www.ietf.org and navigate to Working >Groups). > >> >>What does this mean to us? Not
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
At 6:19 PM + 2/19/03, Vicky Rode wrote: >comments in-line: > > >-Original Message- >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of >Kelly Cobean >Sent: Tuesday, February 18, 2003 7:54 PM >To: [EMAIL PROTECTED] >Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > >Priscilla, > Ok, you caught me not telling the whole truth. There is a second VLAN >on the switch, but my point was that the MLS cache is full of entries for >one host talking to another host off of the same VLAN interface but on a >secondary subnet, indicating that L3 switching (routing) took place for that >data-flow...So now I guess there are two hands clapping ;-) You sure do >keep us all on our toes!!! Thanks! >- >that's because packet switching between subnets using secondaries are >process-switched. On general IOS -- can't speak to the switch implementations -- you can code ip route-cache same-interface ipx route-cache same-interface and get fast switching for secondaries. Don't know if there is a way for CEF to figure this out. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63385&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
comments in-line: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Howard C. Berkowitz Sent: Tuesday, February 18, 2003 6:42 AM To: [EMAIL PROTECTED] Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] At 5:30 AM + 2/18/03, Ken Diliberto wrote: >The nit I'm picking is inline... (I'm feeling like chipping in tonight) > >>>> "The Long and Winding Road" >02/17/03 06:13PM >>> > >[snip] > >if I have a 75xx router with 300 ethernet ports, and I bridge all >those >ports, do I have an L3 switch, or a router? > >[KD] >You have a router performing L2 operations (forwarding, switching, >bridging -- whatever). Would a cheap Linksys switch be faster? > >What makes a L3 switch in my mind is where the forwarding happens. If >the L3 CPU (new way to look at it?) has to handle every packet, that's a >router. If the first L3 packet is handled by the CPU which then >programs ASICs to handle the rest of the flow without bothering the CPU, >that's an L3 switch. Is there a difference from a packet/network >perspective? No. The L2 headers and L3 headers are all properly >updated in both cases (at least we *hope* they are) and traffic is >delivered most of the time. (If it was delivered all the time, networks >wouldn't need us to fix them) :-) Does that make a 7500 with VIPs a L3 switch? A 12000 with distributed forwarding processors? -- it dependscall it (d)cef switching router if you want but i have to kinda agree with ken's comments. in my opinion the major difference between a tradition router and a l3 switch is the way packet switching takes place. in a tradition router the packet switching are done in software (microprocessor based), whereas in l3 switch it is done by asic in hw and mls is used to increase routing performance by doing packet switching and rewrites in hw (asics). that's all. regards, /vicky Substituting router for L3 switch is a good idea, but go farther than that. You can think of a high-performance router as a small hidden network, containing one or more (think high availability) path determination "routing" processors/hosts that download FIB information to multiple forwarding processors/hosts. One public and vendor-independent discussion of this architecture continues in the IETF FORCES Working Group (go to www.ietf.org and navigate to Working Groups). > >What does this mean to us? Not much other than for capacity planning. >IMHO, an L3 switch has a longer life than a router. Not really, as you say in your next paragraph. I could go off into the ozone and say all high-speed routers are L3 switches. Indeed, ASICs aren't a necessity. I've worked on research router designs that used RISC processors in each forwarding and path determination engine, which gave lots of power but much more flexibility than ASICs. Admittedly, at least one of these was a specifically designed processor, but it definitely was software loadable and ran a real time OS. ASIC gets blurry anyway, when you start getting into the pure hard-etched IC, field-programmable gate arrays, electrically alterable field-programmable gate arrays, microcode sequencers, etc. > >When I design networks, I don't think L3 switch. I think about routers >interconnecting L2 segments. I even draw them that way most of the >time. :-) > >My advice to those having problems with this subject: Replace every >occurrence of "layer 3 switch" with "router". > [/KD] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63372&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
comments in-line: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Kelly Cobean Sent: Tuesday, February 18, 2003 7:54 PM To: [EMAIL PROTECTED] Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] Priscilla, Ok, you caught me not telling the whole truth. There is a second VLAN on the switch, but my point was that the MLS cache is full of entries for one host talking to another host off of the same VLAN interface but on a secondary subnet, indicating that L3 switching (routing) took place for that data-flow...So now I guess there are two hands clapping ;-) You sure do keep us all on our toes!!! Thanks! - that's because packet switching between subnets using secondaries are process-switched. regards, /vicky -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Tuesday, February 18, 2003 1:08 AM To: [EMAIL PROTECTED] Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] I'm loath to continue this discussion, but I do have a question for Kelly. Why do you have a VLAN at all in your example?? Isn't a single VLAN sort of like one hand clapping? Seriously, what role is it playing in your network? Of course you don't have to have VLANs to do routing/L3 switching, as you probabaly know. But maybe there's some weird configuration gotcha, specific to the 6509? Just curious. Thanks. Larry said the majority of the Cisco campus is networked with L3 switches and not using vlans. That says a lot right there! Priscilla Kelly Cobean wrote: > > All, >I'd like to add to this something that I haven't seen in > other posts yet, > and that is a quick look at layer2 function. I have a Catalyst > 6509 with an > MSFC on it. There is only *ONE* VLAN configured on the MSFC, > however, that > VLAN has several secondary addresses assigned to it (I know, > not a great > solution, but let's not go there). If I do a "show mls entry" > on my switch, > it is full of entries for hosts talking to hosts on the same > VLAN. My > point? When a host wants to talk to a host on another subnet > (VLAN or not), > it ANDs the address with it's own mask, determines that the > host is in fact > on a different subnet, then arps (if necessary) for it's > default gateway > (the MSFC) and sends the packet on it's way. The 6509/MSFC > receive the > packet and begin the MLS cache setup process (candidate packet, > timeout, > etc). All this is still done inspite of the fact that the MSFC > only has a > single VLAN. > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > Behalf Of > Stephen Hoover > Sent: Monday, February 17, 2003 8:33 PM > To: [EMAIL PROTECTED] > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > [7:63147] > > > > > - > > > actually it is by doing secondaries, but i would highly > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > one may also configure the physical interfaces as L3 > interfaces - just as > > one might do on a router with several ethernet ports. > > > Oo ok, now THAT statement leads me to believe the L3 > switching IS > possible without VLANs. > > > -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63371&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Howard, It would be so much fun to not understand some of this up close. :-) >>> "Howard C. Berkowitz" 02/18/03 06:42AM >>> [snip] Does that make a 7500 with VIPs a L3 switch? A 12000 with distributed forwarding processors? Substituting router for L3 switch is a good idea, but go farther than that. You can think of a high-performance router as a small hidden network, containing one or more (think high availability) path determination "routing" processors/hosts that download FIB information to multiple forwarding processors/hosts. One public and vendor-independent discussion of this architecture continues in the IETF FORCES Working Group (go to www.ietf.org and navigate to Working Groups). > >What does this mean to us? Not much other than for capacity planning. >IMHO, an L3 switch has a longer life than a router. Not really, as you say in your next paragraph. I could go off into the ozone and say all high-speed routers are L3 switches. Indeed, ASICs aren't a necessity. I've worked on research router designs that used RISC processors in each forwarding and path determination engine, which gave lots of power but much more flexibility than ASICs. Admittedly, at least one of these was a specifically designed processor, but it definitely was software loadable and ran a real time OS. ASIC gets blurry anyway, when you start getting into the pure hard-etched IC, field-programmable gate arrays, electrically alterable field-programmable gate arrays, microcode sequencers, etc. [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63323&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching [7:63304]
Han Chuan Alex Ang wrote: > > hi, I am trying to have a clearer picture of the layer 3 > switching > > concept. > > Assuming that I have a Core Catalyst 6 series switch with layer > 3 > > switching capabilities, I have a Access layer switch connected > to the > > core with two port label Vlan 1 subnet 1 and Vlan 2 subnet 2, > > when frames is sent from from Vlan 1 to Vlan 2 on the same > Access > > switch, my understanding is that for layer 3 switching , it > will > > evoke a route one and switch the rest concept , Layer 3 switching just means routing. What you're talking about is an advanced feature of some switches whereby the L3 core switch can tell the L2 access switch how to encapsulate and forward the packets for this flow on its own in the future. This is sometimes called distributed switching or multi-layer switching, although both those terms get used in other ways too. Many Cisco switches don't support this, but some do. Both the core and the access switch would have to support this advanced feature for it to work. The Catalyst 6000 does support it. The L3 core switch has a route processor in it. It acts as a router. It talks to the L2 access switch's switching engine with a protocol such as Cisco's Multilayer Switching Protocol (MLSP) to let the L2 switch know how to handle the packets in the future. Architecturally it's no different than a router that has a route processor and a forwarding engine, except that now the jobs are being done in two boxes. It's not accurate to equate this behavior with L3 switching. It's more accuate to say this behavior is one feature of some advanced L3 switches. Notice that it requires an additional protocol. It also requires quite a few non-default configuration commands. Priscilla > my question is > that, > > after the first route , if no Access list has been created, > will the > > the Access switch be smart enough to perform internal > > switching, that is , frame direct from Vlan 1 to Vlan 2 > internally > > within the Access switch. If the answer is no, Are there > switches on > > the market that is routing by this concept, please advice , > > thanks to all the guys who have tried to entertain all my > questions > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63317&t=63304 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Layer 3 switching [7:63304]
At 1:57 AM + 2/19/03, Han Chuan Alex Ang wrote: >hi, I am trying to have a clearer picture of the layer 3 switching > >concept. > >Assuming that I have a Core Catalyst 6 series switch with layer 3 > >switching capabilities, I have a Access layer switch connected to the > >core with two port label Vlan 1 subnet 1 and Vlan 2 subnet 2, > >when frames is sent from from Vlan 1 to Vlan 2 on the same Access > >switch, my understanding is that for layer 3 switching , it will > >evoke a route one and switch the rest concept , my question is that, > >after the first route , if no Access list has been created, will the > >the Access switch be smart enough to perform internal > >switching, that is , frame direct from Vlan 1 to Vlan 2 internally > >within the Access switch. I'm not sure exactly what you are describing, but the first question in my mind is what MAC address would be in the source field of the frame going to VLAN 2. Could make for some pretty confused ARP tables. Would the IP address have to be rewritten if it now corresponds to a different MAC address? >If the answer is no, Are there switches on > >the market that is routing by this concept, please advice , What problem are you trying to solve? I can't see the difference as involving any significant delay, and I still don't quite see what the subnet relationships will be. > >thanks to all the guys who have tried to entertain all my questions Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63319&t=63304 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Priscilla, Ok, you caught me not telling the whole truth. There is a second VLAN on the switch, but my point was that the MLS cache is full of entries for one host talking to another host off of the same VLAN interface but on a secondary subnet, indicating that L3 switching (routing) took place for that data-flow...So now I guess there are two hands clapping ;-) You sure do keep us all on our toes!!! Thanks! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Tuesday, February 18, 2003 1:08 AM To: [EMAIL PROTECTED] Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] I'm loath to continue this discussion, but I do have a question for Kelly. Why do you have a VLAN at all in your example?? Isn't a single VLAN sort of like one hand clapping? Seriously, what role is it playing in your network? Of course you don't have to have VLANs to do routing/L3 switching, as you probabaly know. But maybe there's some weird configuration gotcha, specific to the 6509? Just curious. Thanks. Larry said the majority of the Cisco campus is networked with L3 switches and not using vlans. That says a lot right there! Priscilla Kelly Cobean wrote: > > All, >I'd like to add to this something that I haven't seen in > other posts yet, > and that is a quick look at layer2 function. I have a Catalyst > 6509 with an > MSFC on it. There is only *ONE* VLAN configured on the MSFC, > however, that > VLAN has several secondary addresses assigned to it (I know, > not a great > solution, but let's not go there). If I do a "show mls entry" > on my switch, > it is full of entries for hosts talking to hosts on the same > VLAN. My > point? When a host wants to talk to a host on another subnet > (VLAN or not), > it ANDs the address with it's own mask, determines that the > host is in fact > on a different subnet, then arps (if necessary) for it's > default gateway > (the MSFC) and sends the packet on it's way. The 6509/MSFC > receive the > packet and begin the MLS cache setup process (candidate packet, > timeout, > etc). All this is still done inspite of the fact that the MSFC > only has a > single VLAN. > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > Behalf Of > Stephen Hoover > Sent: Monday, February 17, 2003 8:33 PM > To: [EMAIL PROTECTED] > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > [7:63147] > > > > > - > > > actually it is by doing secondaries, but i would highly > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > one may also configure the physical interfaces as L3 > interfaces - just as > > one might do on a router with several ethernet ports. > > > Oo ok, now THAT statement leads me to believe the L3 > switching IS > possible without VLANs. > > > -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63316&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Layer 3 switching [7:63304]
I'm fairly certain the answer to your first question is no, the switch will not be intelligent enough to switch it to the appropriate port automatically. The reason is that the switch must go through a layer 3 device to get from one VLAN (aka IP subnet) to another. I don't think this is a real issue since the rest of the traffic is switched at wire speed, introducing very little (almost no) latency. There are however switches on the market, even by Cisco that will do this. Any layer 3 switch will do. For example, the Cisco 2948G-L3 switch. Check out their website under "Products and Technologies" for more information. ""Han Chuan Alex Ang"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > hi, I am trying to have a clearer picture of the layer 3 switching > > concept. > > Assuming that I have a Core Catalyst 6 series switch with layer 3 > > switching capabilities, I have a Access layer switch connected to the > > core with two port label Vlan 1 subnet 1 and Vlan 2 subnet 2, > > when frames is sent from from Vlan 1 to Vlan 2 on the same Access > > switch, my understanding is that for layer 3 switching , it will > > evoke a route one and switch the rest concept , my question is that, > > after the first route , if no Access list has been created, will the > > the Access switch be smart enough to perform internal > > switching, that is , frame direct from Vlan 1 to Vlan 2 internally > > within the Access switch. If the answer is no, Are there switches on > > the market that is routing by this concept, please advice , > > thanks to all the guys who have tried to entertain all my questions Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63312&t=63304 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
""Ken Diliberto"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Priscilla, > > All I want is credit. :-) if it makes you feel better, Ken, I always credit you with at least two cents worth I'm going to be visiting some of your compadres int the next couple of weeks. Dare I drop your name? ;-> > > "Some guy on one of the many mailling lists I frequent put it this > way:" (maybe not) > > Ken > > >>> "Priscilla Oppenheimer" 02/18/03 12:06PM > >>> > [snip] > > I think Ken's example is one of the cleanest I've seen. I may have to > borrow it for my classes. > > [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63305&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Layer 3 switching [7:63304]
hi, I am trying to have a clearer picture of the layer 3 switching concept. Assuming that I have a Core Catalyst 6 series switch with layer 3 switching capabilities, I have a Access layer switch connected to the core with two port label Vlan 1 subnet 1 and Vlan 2 subnet 2, when frames is sent from from Vlan 1 to Vlan 2 on the same Access switch, my understanding is that for layer 3 switching , it will evoke a route one and switch the rest concept , my question is that, after the first route , if no Access list has been created, will the the Access switch be smart enough to perform internal switching, that is , frame direct from Vlan 1 to Vlan 2 internally within the Access switch. If the answer is no, Are there switches on the market that is routing by this concept, please advice , thanks to all the guys who have tried to entertain all my questions Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63304&t=63304 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Priscilla, All I want is credit. :-) "Some guy on one of the many mailling lists I frequent put it this way:" (maybe not) Ken >>> "Priscilla Oppenheimer" 02/18/03 12:06PM >>> [snip] I think Ken's example is one of the cleanest I've seen. I may have to borrow it for my classes. [snip] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63303&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Stephen Hoover wrote: > > Ken, > > Thanks for the input on this discussion. I follow and > understand your > example without any problems. > > Now if taking it back to the original original question - > Does L3 > switching require VLANs - produces this question for your > example: > > You state 1 fiber feed for both Science and Engineering in > the Labs > building. I am then assuming that they are all connected to the > same set of > switches (Layer 2) in that building. > Could you have not just simply assigned the hosts for > Science to 1 IP > network and the hosts for Engineering to another IP network - > then created > respective gateway interfaces for each network back on the > common Layer 3 > switch and accomplished the same thing?? It depends on the meaning of "thing" in your "accomplish the same thing" comment. :-) I think you already figured out your confusion and maybe this message is old, but I'll reply just in case. With your design you would accomplish connectivity. However, you would not accomplish separation of broadcast traffic for the two user communities. VLANs in the L2-switched part of the network give you that. VLANs have lots of features, but that's one of their primary ones. I think Ken's example is one of the cleanest I've seen. I may have to borrow it for my classes. Thanks for a good discussion, Stephen. THE END (hopefully! :-) Priscilla > > If the answer is yes, I will followup with another > question. If the > answer is no, then please explain. > > Thanks!! > > Stephen > - Original Message - > From: "Ken Diliberto" > To: > Sent: Tuesday, February 18, 2003 12:24 AM > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > [7:63147] > > > > Stephen, > > > > You're getting there. Let me give an example of how VLANs > are used > > (I'd draw a picture, but it probably wouldn't look good). > > > > For this example, let's use two of the colleges on my > university > > network: Science and Engineering. > > > > Each has their own block of IP addresses and want their > traffic > > separate from the other. They also want flat addressing (no > > subnetting). > > > > We have three buildings: Science, Engineering and Labs. > Science and > > Engineering both have computer labs in the Labs building. > Each want > > their labs on their respective IP address blocks. > > > > If money were no object, this would be fairly easy with > vanilla > > switches and a router with two ethernet interfaces. Multiple > fiber > > feeds and two sets of switches would be everywhere. > > > > With budget limitations (for this example), we only have a > single fiber > > feed to each location. That means each fiber feed needs to > carry > > traffic for both networks. To keep the traffic separate, we > partition > > the switch ports into two LANs: LAN 10 and LAN 20. These two > LANs in > > one switch are treated as unique. To do this, the switch > creates > > Virtual LANs or VLANs. The fiber feeds are now trunks > because a header > > is added to each frame to identify the VLAN it belongs to. > > > > So far so good? > > > > Why would we need a router? To talk between VLANs. > > > > Do routers understand trunks? Yes. > > > > This brings up one more concept: the Router on a Stick. > > > > A router on a stick is a router with a single network > connection. This > > single connection is configured as a trunk so the router can > see all the > > different VLANs. If the router finds a packet on VLAN 10 > with a > > destination on VLAN 20, it rewrites the headers for the > destination and > > puts it back on the same trunk with VLAN 20 headers. > > > > Remember: replace "layer 3 switch" with "router" every time > you see > > it. That might make more sense. > > > > Hope this helps. > > > > Ken > > > > >>> "Stephen Hoover" 02/17/03 > 06:55PM >>> > > I appreciate everyone's input on this subject to help me > understand > > this > > concept. > > > > As far as the newbies comment goes - I most definitely am. > I'm about > > as > > green as they come. I have both my CCNA and my CCDA, but my > only real > > experience is installing 2 T1s (at different locations) and > configuring > > NAT > > for them. I have large amount of knowledge, just no > experience. It has > > been > > my go
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Stephen Hoover wrote: > > Ken, > > Thanks for the input on this discussion. I follow and > understand your > example without any problems. > > Now if taking it back to the original original question - > Does L3 > switching require VLANs - produces this question for your > example: > > You state 1 fiber feed for both Science and Engineering in > the Labs > building. I am then assuming that they are all connected to the > same set of > switches (Layer 2) in that building. > Could you have not just simply assigned the hosts for > Science to 1 IP > network and the hosts for Engineering to another IP network - > then created > respective gateway interfaces for each network back on the > common Layer 3 > switch and accomplished the same thing?? It depends on the meaning of "thing" in your "accomplish the same thing" comment. :-) I think you already figured out your confusion and maybe this message is old, but I'll reply just in case. With your design you would accomplish connectivity. However, you would not accomplish separation of broadcast traffic for the two user communities. VLANs in the L2-switched part of the network give you that. VLANs have lots of features, but that's one of their primary ones. I think Ken's example is one of the cleanest I've seen. I may have to borrow it for my classes. Thanks for a good discussion, Stephen. THE END (hopefully! :-) Priscilla > > If the answer is yes, I will followup with another > question. If the > answer is no, then please explain. > > Thanks!! > > Stephen > - Original Message - > From: "Ken Diliberto" > To: > Sent: Tuesday, February 18, 2003 12:24 AM > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > [7:63147] > > > > Stephen, > > > > You're getting there. Let me give an example of how VLANs > are used > > (I'd draw a picture, but it probably wouldn't look good). > > > > For this example, let's use two of the colleges on my > university > > network: Science and Engineering. > > > > Each has their own block of IP addresses and want their > traffic > > separate from the other. They also want flat addressing (no > > subnetting). > > > > We have three buildings: Science, Engineering and Labs. > Science and > > Engineering both have computer labs in the Labs building. > Each want > > their labs on their respective IP address blocks. > > > > If money were no object, this would be fairly easy with > vanilla > > switches and a router with two ethernet interfaces. Multiple > fiber > > feeds and two sets of switches would be everywhere. > > > > With budget limitations (for this example), we only have a > single fiber > > feed to each location. That means each fiber feed needs to > carry > > traffic for both networks. To keep the traffic separate, we > partition > > the switch ports into two LANs: LAN 10 and LAN 20. These two > LANs in > > one switch are treated as unique. To do this, the switch > creates > > Virtual LANs or VLANs. The fiber feeds are now trunks > because a header > > is added to each frame to identify the VLAN it belongs to. > > > > So far so good? > > > > Why would we need a router? To talk between VLANs. > > > > Do routers understand trunks? Yes. > > > > This brings up one more concept: the Router on a Stick. > > > > A router on a stick is a router with a single network > connection. This > > single connection is configured as a trunk so the router can > see all the > > different VLANs. If the router finds a packet on VLAN 10 > with a > > destination on VLAN 20, it rewrites the headers for the > destination and > > puts it back on the same trunk with VLAN 20 headers. > > > > Remember: replace "layer 3 switch" with "router" every time > you see > > it. That might make more sense. > > > > Hope this helps. > > > > Ken > > > > >>> "Stephen Hoover" 02/17/03 > 06:55PM >>> > > I appreciate everyone's input on this subject to help me > understand > > this > > concept. > > > > As far as the newbies comment goes - I most definitely am. > I'm about > > as > > green as they come. I have both my CCNA and my CCDA, but my > only real > > experience is installing 2 T1s (at different locations) and > configuring > > NAT > > for them. I have large amount of knowledge, just no > experience. It has > > been > > my go
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
At 5:30 AM + 2/18/03, Ken Diliberto wrote: >The nit I'm picking is inline... (I'm feeling like chipping in tonight) > "The Long and Winding Road" >02/17/03 06:13PM >>> > >[snip] > >if I have a 75xx router with 300 ethernet ports, and I bridge all >those >ports, do I have an L3 switch, or a router? > >[KD] >You have a router performing L2 operations (forwarding, switching, >bridging -- whatever). Would a cheap Linksys switch be faster? > >What makes a L3 switch in my mind is where the forwarding happens. If >the L3 CPU (new way to look at it?) has to handle every packet, that's a >router. If the first L3 packet is handled by the CPU which then >programs ASICs to handle the rest of the flow without bothering the CPU, >that's an L3 switch. Is there a difference from a packet/network >perspective? No. The L2 headers and L3 headers are all properly >updated in both cases (at least we *hope* they are) and traffic is >delivered most of the time. (If it was delivered all the time, networks >wouldn't need us to fix them) :-) Does that make a 7500 with VIPs a L3 switch? A 12000 with distributed forwarding processors? Substituting router for L3 switch is a good idea, but go farther than that. You can think of a high-performance router as a small hidden network, containing one or more (think high availability) path determination "routing" processors/hosts that download FIB information to multiple forwarding processors/hosts. One public and vendor-independent discussion of this architecture continues in the IETF FORCES Working Group (go to www.ietf.org and navigate to Working Groups). > >What does this mean to us? Not much other than for capacity planning. >IMHO, an L3 switch has a longer life than a router. Not really, as you say in your next paragraph. I could go off into the ozone and say all high-speed routers are L3 switches. Indeed, ASICs aren't a necessity. I've worked on research router designs that used RISC processors in each forwarding and path determination engine, which gave lots of power but much more flexibility than ASICs. Admittedly, at least one of these was a specifically designed processor, but it definitely was software loadable and ran a real time OS. ASIC gets blurry anyway, when you start getting into the pure hard-etched IC, field-programmable gate arrays, electrically alterable field-programmable gate arrays, microcode sequencers, etc. > >When I design networks, I don't think L3 switch. I think about routers >interconnecting L2 segments. I even draw them that way most of the >time. :-) > >My advice to those having problems with this subject: Replace every >occurrence of "layer 3 switch" with "router". > [/KD] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63260&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
>"Vicky Rode" shaped photons and electrons to say: > > >see comments in-line: > > >-Original Message- >From: Stephen Hoover [mailto:[EMAIL PROTECTED]] >Sent: Monday, February 17, 2003 11:20 AM >To: Vicky Rode >Cc: [EMAIL PROTECTED] >Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > >> > Say for instance I have 2 hosts on the same layer 3 switch, but the > >two >> hosts are on 2 different IP subnets (No VLANs are defined). >> >> That's not possible! if you are talking about 2 IP subnet, than: >> - >> actually it is by doing secondaries, but i would highly recommend doing >> vlans if possible. keep it clean and simple. >> > > >Vicki, > > You mention the use of secondary IP's. On a L3 switch (a switch with the >router engine in it) is it not possible to define Ethernet sub interfaces >instead of using secondary IPs - without VLANs defined? Yes and no. Secondaries and VLANs serve different purposes. Basic IP assumption:1 physical medium[1] = 1 subnet Secondary assumption: 1 physical medium[2] = multiple subnets Basic VLAN assumption: multiple phyical media [3] = 1 subnet VLAN with secondaries: multiple physical media = multiple subnets on all Notes - [1] Based on the "local versus remote" IP assumption: if a host is on your subnet, you have layer 2 connectivity to it. if a host is on a different subnet, you need to reach it through a router. This works nicely for broadcast and point-to-point media. NBMA and demand circuits break the local-vs-remote assumption. If you do assume a broadcast* medium, then the physical medium = 1 broadcast domain = 1 subnet (* broadcast is used loosely -- multicast is often closer. Some stupid NICs don't recognize multicasts and treat all multicasts as a broadcast. Broadcasts, indeed, are special cases of multicasts.) [2] The medium simultaneously must support a broadcast domain for each subnet, unless it is a non-broadcast medium. [3] The media in different locations are assumed to be linked by L2** trunking, typically IEEE 802.1q. While the trunks do contain traffic from multiple subnets, they are effectively tunneled. The only multicasts on the trunk medium are for layer management functions, such as 802.1d, 802.1q, VTP, etc. (** there are exotic variants where you could carry trunking over a conventionally routed tunnel, but let's not go there.) > >yes you can but when you create sub-interfaces it ask for encapsulation type >and this is where vlans come into play. Encapsulation type is one reason to use VLANs, because it does create different broadcast domains for each encapsulation. This is preferred, but Cisco certainly has supported secondaries for different encapsulations -- more an IPX than an IP support technique. >whereas with secondaries it will >route between the subnets. > > > > I'm sorry to be so thick, I'm just not getting it. If a L3 switch (with >a routing module/engine in it) is essentially a wire speed router, then the >VLAN just seems like an additional identifier on top of the L3 address - and >doesn't really serve any purpose. Not exactly. It lets you have the _same_ broadcast domain in several L2 switches. That's what gives you the portability of hosts from VLAN (same subnet) to same VLAN in different buildings. There need be only one router on the subnet, but there can be multiple VLAN segments connected by trunking. >In my previous example, 2 hosts on the >same L3 switch, but on 2 different IP subnets - wouldn't a defined Ethernet >subinterface be each clients respective gateway, and thus normal L3 routing >would occur, just at switch speeds >- >well let me you ask this, why not just supernet and put all stations on >the same subnet (don't do this i'm being facetious). > >that's because you do not want to create this huge broadcast domain. that's >the whole purpose of having vlans. > >if this still doesn't make sense, feel free to ask...would love to help. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63259&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Layer 3 switching and VLANs - an epiphany [7:63240]
your still a little off target... Layer 2 interfaces can be access ports or trunks for vlans Layer 2 or Layer 3 switch interfaces dont need to be sub-interfaces.. Layer 3 vlan interfaces(svi) require layer 2 trunk interfaces to interconnect vlans in other switches Layer 3 interfaces only require an ip address and routing support to make them function Larry Letterman Network Engineer Cisco Systems - Original Message - From: "Stephen Hoover" To: > Layer 3 switching does not require VLANs, but what is DOES require is a > physical port connection on the common L3 switch for every IP network that > is connected to the L2 switches. (Hosts on the same L2 switch that are > configured to be in 2 different IP networks.) This is not always possible > nor administratively friendly. > > With VLANs, you can create the equivalent of sub interfaces on a single port > on the L3 switch - hence trunking. You cannot trunk multiple IP networks > (without VLANs) on a single port connection the L3 switch, because you > cannot create Ethernet sub-interfaces... > > That's where I was missing it. > > I think it both Vicki and Jens mentioned something about this. > > Of course if I am off-kilter here, someone please slap me about :) Otherwise > I am confident this is where my misunderstanding really occurred. > > Thanks to EVERYONE who responded - you are all a great group of people to > stick it out until this was beat into my thick skull!!! > > Stephen Hoover > Dallas, Texas [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63243&t=63240 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
I have a data center on the cisco campus that has well over 80 subnets in it, using L3 routing and no vlans on the 6509 gateways(routers).. We also have a production data center that uses 6509's with vlans that span different areas in the data center...due to the application structure of the servers and the fact that a lot of the servers have a need for redundant nics ... It works both ways folks...depends on what the need is Larry Letterman Network Engineer Cisco Systems - Original Message - From: "Priscilla Oppenheimer" To: Sent: Monday, February 17, 2003 10:07 PM Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] > I'm loath to continue this discussion, but I do have a question for Kelly. > Why do you have a VLAN at all in your example?? Isn't a single VLAN sort of > like one hand clapping? Seriously, what role is it playing in your network? > > Of course you don't have to have VLANs to do routing/L3 switching, as you > probabaly know. But maybe there's some weird configuration gotcha, specific > to the 6509? Just curious. Thanks. > > Larry said the majority of the Cisco campus is networked with L3 switches > and not using vlans. That says a lot right there! > > Priscilla > > Kelly Cobean wrote: > > > > All, > >I'd like to add to this something that I haven't seen in > > other posts yet, > > and that is a quick look at layer2 function. I have a Catalyst > > 6509 with an > > MSFC on it. There is only *ONE* VLAN configured on the MSFC, > > however, that > > VLAN has several secondary addresses assigned to it (I know, > > not a great > > solution, but let's not go there). If I do a "show mls entry" > > on my switch, > > it is full of entries for hosts talking to hosts on the same > > VLAN. My > > point? When a host wants to talk to a host on another subnet > > (VLAN or not), > > it ANDs the address with it's own mask, determines that the > > host is in fact > > on a different subnet, then arps (if necessary) for it's > > default gateway > > (the MSFC) and sends the packet on it's way. The 6509/MSFC > > receive the > > packet and begin the MLS cache setup process (candidate packet, > > timeout, > > etc). All this is still done inspite of the fact that the MSFC > > only has a > > single VLAN. > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > > Behalf Of > > Stephen Hoover > > Sent: Monday, February 17, 2003 8:33 PM > > To: [EMAIL PROTECTED] > > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > > [7:63147] > > > > > > > > - > > > > actually it is by doing secondaries, but i would highly > > recommend doing > > > > vlans if possible. keep it clean and simple. > > > > > > > > > one may also configure the physical interfaces as L3 > > interfaces - just as > > > one might do on a router with several ethernet ports. > > > > > > Oo ok, now THAT statement leads me to believe the L3 > > switching IS > > possible without VLANs. > > > > > > -Stephen [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63241&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Layer 3 switching and VLANs - an epiphany [7:63240]
Ok, its 1:29AM CST - and I am setting here chewing on this switching study guide information about VLANs. I think I see where my confusion has come from and what the answer is now. Layer 3 switching does not require VLANs, but what is DOES require is a physical port connection on the common L3 switch for every IP network that is connected to the L2 switches. (Hosts on the same L2 switch that are configured to be in 2 different IP networks.) This is not always possible nor administratively friendly. With VLANs, you can create the equivalent of sub interfaces on a single port on the L3 switch - hence trunking. You cannot trunk multiple IP networks (without VLANs) on a single port connection the L3 switch, because you cannot create Ethernet sub-interfaces... That's where I was missing it. I think it both Vicki and Jens mentioned something about this. Of course if I am off-kilter here, someone please slap me about :) Otherwise I am confident this is where my misunderstanding really occurred. Thanks to EVERYONE who responded - you are all a great group of people to stick it out until this was beat into my thick skull!!! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63240&t=63240 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
Ken, Thanks for the input on this discussion. I follow and understand your example without any problems. Now if taking it back to the original original question - Does L3 switching require VLANs - produces this question for your example: You state 1 fiber feed for both Science and Engineering in the Labs building. I am then assuming that they are all connected to the same set of switches (Layer 2) in that building. Could you have not just simply assigned the hosts for Science to 1 IP network and the hosts for Engineering to another IP network - then created respective gateway interfaces for each network back on the common Layer 3 switch and accomplished the same thing?? If the answer is yes, I will followup with another question. If the answer is no, then please explain. Thanks!! Stephen - Original Message - From: "Ken Diliberto" To: Sent: Tuesday, February 18, 2003 12:24 AM Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > Stephen, > > You're getting there. Let me give an example of how VLANs are used > (I'd draw a picture, but it probably wouldn't look good). > > For this example, let's use two of the colleges on my university > network: Science and Engineering. > > Each has their own block of IP addresses and want their traffic > separate from the other. They also want flat addressing (no > subnetting). > > We have three buildings: Science, Engineering and Labs. Science and > Engineering both have computer labs in the Labs building. Each want > their labs on their respective IP address blocks. > > If money were no object, this would be fairly easy with vanilla > switches and a router with two ethernet interfaces. Multiple fiber > feeds and two sets of switches would be everywhere. > > With budget limitations (for this example), we only have a single fiber > feed to each location. That means each fiber feed needs to carry > traffic for both networks. To keep the traffic separate, we partition > the switch ports into two LANs: LAN 10 and LAN 20. These two LANs in > one switch are treated as unique. To do this, the switch creates > Virtual LANs or VLANs. The fiber feeds are now trunks because a header > is added to each frame to identify the VLAN it belongs to. > > So far so good? > > Why would we need a router? To talk between VLANs. > > Do routers understand trunks? Yes. > > This brings up one more concept: the Router on a Stick. > > A router on a stick is a router with a single network connection. This > single connection is configured as a trunk so the router can see all the > different VLANs. If the router finds a packet on VLAN 10 with a > destination on VLAN 20, it rewrites the headers for the destination and > puts it back on the same trunk with VLAN 20 headers. > > Remember: replace "layer 3 switch" with "router" every time you see > it. That might make more sense. > > Hope this helps. > > Ken > > >>> "Stephen Hoover" 02/17/03 06:55PM >>> > I appreciate everyone's input on this subject to help me understand > this > concept. > > As far as the newbies comment goes - I most definitely am. I'm about > as > green as they come. I have both my CCNA and my CCDA, but my only real > experience is installing 2 T1s (at different locations) and configuring > NAT > for them. I have large amount of knowledge, just no experience. It has > been > my goal and my dream to become a serious network engineer for the last > 6 > years, but I just cannot seem to get a job that offers any experience. > Everytime I get a "network" position, I just seemed to end up doing > desktop > support. > > When I first heard the term Layer 3 switching (some 4 years ago now) > the > first thing that popped into my mind was a switch that can route. I > never > even heard of a VLAN until a couple of years ago. > > The Cisco Study guide starts off talking about VLANs, and moves right > into > Inter-VLAN routing without ever really discussing Layer 3 switching as > a > seperate process. This is really where my confusion started. The book > makes > it sound like L3 switching is directly dependent on VLANs, and I just > didn't > see it - it wasn't something I was just willing to accept. > > Further more, the book states that VLANs allow for physical location > independence, but is also says that VLANs should not cross the core - > those > 2 statements seem partly contradictory to me. > > Here is a summary of how I see VLANs now. > > Layer 3 switching is possible without VLANs (however the opposite is > not > true. Well at least not without some form of Layer 3 intervention.) >
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I'm loath to continue this discussion, but I do have a question for Kelly. > Why do you have a VLAN at all in your example?? Isn't a single VLAN sort of > like one hand clapping? Seriously, what role is it playing in your network? said half seriously, isn't a network with NO vlans no different than a network with ONE vlan? ;-> > > Of course you don't have to have VLANs to do routing/L3 switching, as you > probabaly know. But maybe there's some weird configuration gotcha, specific > to the 6509? Just curious. Thanks. > > Larry said the majority of the Cisco campus is networked with L3 switches > and not using vlans. That says a lot right there! > > Priscilla > > Kelly Cobean wrote: > > > > All, > >I'd like to add to this something that I haven't seen in > > other posts yet, > > and that is a quick look at layer2 function. I have a Catalyst > > 6509 with an > > MSFC on it. There is only *ONE* VLAN configured on the MSFC, > > however, that > > VLAN has several secondary addresses assigned to it (I know, > > not a great > > solution, but let's not go there). If I do a "show mls entry" > > on my switch, > > it is full of entries for hosts talking to hosts on the same > > VLAN. My > > point? When a host wants to talk to a host on another subnet > > (VLAN or not), > > it ANDs the address with it's own mask, determines that the > > host is in fact > > on a different subnet, then arps (if necessary) for it's > > default gateway > > (the MSFC) and sends the packet on it's way. The 6509/MSFC > > receive the > > packet and begin the MLS cache setup process (candidate packet, > > timeout, > > etc). All this is still done inspite of the fact that the MSFC > > only has a > > single VLAN. > > > > -Original Message- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > > Behalf Of > > Stephen Hoover > > Sent: Monday, February 17, 2003 8:33 PM > > To: [EMAIL PROTECTED] > > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > > [7:63147] > > > > > > > > - > > > > actually it is by doing secondaries, but i would highly > > recommend doing > > > > vlans if possible. keep it clean and simple. > > > > > > > > > one may also configure the physical interfaces as L3 > > interfaces - just as > > > one might do on a router with several ethernet ports. > > > > > > Oo ok, now THAT statement leads me to believe the L3 > > switching IS > > possible without VLANs. > > > > > > -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63235&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
I'm loath to continue this discussion, but I do have a question for Kelly. Why do you have a VLAN at all in your example?? Isn't a single VLAN sort of like one hand clapping? Seriously, what role is it playing in your network? Of course you don't have to have VLANs to do routing/L3 switching, as you probabaly know. But maybe there's some weird configuration gotcha, specific to the 6509? Just curious. Thanks. Larry said the majority of the Cisco campus is networked with L3 switches and not using vlans. That says a lot right there! Priscilla Kelly Cobean wrote: > > All, >I'd like to add to this something that I haven't seen in > other posts yet, > and that is a quick look at layer2 function. I have a Catalyst > 6509 with an > MSFC on it. There is only *ONE* VLAN configured on the MSFC, > however, that > VLAN has several secondary addresses assigned to it (I know, > not a great > solution, but let's not go there). If I do a "show mls entry" > on my switch, > it is full of entries for hosts talking to hosts on the same > VLAN. My > point? When a host wants to talk to a host on another subnet > (VLAN or not), > it ANDs the address with it's own mask, determines that the > host is in fact > on a different subnet, then arps (if necessary) for it's > default gateway > (the MSFC) and sends the packet on it's way. The 6509/MSFC > receive the > packet and begin the MLS cache setup process (candidate packet, > timeout, > etc). All this is still done inspite of the fact that the MSFC > only has a > single VLAN. > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On > Behalf Of > Stephen Hoover > Sent: Monday, February 17, 2003 8:33 PM > To: [EMAIL PROTECTED] > Subject: Re: Does MLS (Layer 3 switching) require VLANs? > [7:63147] > > > > > - > > > actually it is by doing secondaries, but i would highly > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > one may also configure the physical interfaces as L3 > interfaces - just as > > one might do on a router with several ethernet ports. > > > Oo ok, now THAT statement leads me to believe the L3 > switching IS > possible without VLANs. > > > -Stephen > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63233&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
The nit I'm picking is inline... (I'm feeling like chipping in tonight) >>> "The Long and Winding Road" 02/17/03 06:13PM >>> [snip] if I have a 75xx router with 300 ethernet ports, and I bridge all those ports, do I have an L3 switch, or a router? [KD] You have a router performing L2 operations (forwarding, switching, bridging -- whatever). Would a cheap Linksys switch be faster? What makes a L3 switch in my mind is where the forwarding happens. If the L3 CPU (new way to look at it?) has to handle every packet, that's a router. If the first L3 packet is handled by the CPU which then programs ASICs to handle the rest of the flow without bothering the CPU, that's an L3 switch. Is there a difference from a packet/network perspective? No. The L2 headers and L3 headers are all properly updated in both cases (at least we *hope* they are) and traffic is delivered most of the time. (If it was delivered all the time, networks wouldn't need us to fix them) :-) What does this mean to us? Not much other than for capacity planning. IMHO, an L3 switch has a longer life than a router. When I design networks, I don't think L3 switch. I think about routers interconnecting L2 segments. I even draw them that way most of the time. :-) My advice to those having problems with this subject: Replace every occurrence of "layer 3 switch" with "router". [/KD] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63230&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
> > > - >> > actually it is by doing secondaries, but i would highly recommend doing >> > vlans if possible. keep it clean and simple. >> >> >> one may also configure the physical interfaces as L3 interfaces - just as >> one might do on a router with several ethernet ports. > > >Oo ok, now THAT statement leads me to believe the L3 switching IS >possible without VLANs. > Ouch. L3 switching is routing. Routing interconnects subnets/IP prefixes. If a VLAN is a subnet, it can be routed. If a piece of wire is a subnet, it can be routed. Again: L3 switching is not a technology. It is salesbabble. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63229&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
hi stephen, see comments in-line: -Original Message- From: Stephen Hoover [mailto:[EMAIL PROTECTED]] Sent: Monday, February 17, 2003 11:20 AM To: Vicky Rode Cc: [EMAIL PROTECTED] Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > Say for instance I have 2 hosts on the same layer 3 switch, but the > two > hosts are on 2 different IP subnets (No VLANs are defined). > > That's not possible! if you are talking about 2 IP subnet, than: > - > actually it is by doing secondaries, but i would highly recommend doing > vlans if possible. keep it clean and simple. > Vicki, You mention the use of secondary IP's. On a L3 switch (a switch with the router engine in it) is it not possible to define Ethernet sub interfaces instead of using secondary IPs - without VLANs defined? yes you can but when you create sub-interfaces it ask for encapsulation type and this is where vlans come into play. whereas with secondaries it will route between the subnets. I'm sorry to be so thick, I'm just not getting it. If a L3 switch (with a routing module/engine in it) is essentially a wire speed router, then the VLAN just seems like an additional identifier on top of the L3 address - and doesn't really serve any purpose. In my previous example, 2 hosts on the same L3 switch, but on 2 different IP subnets - wouldn't a defined Ethernet subinterface be each clients respective gateway, and thus normal L3 routing would occur, just at switch speeds - well let me you ask this, why not just supernet and put all stations on the same subnet (don't do this i'm being facetious). that's because you do not want to create this huge broadcast domain. that's the whole purpose of having vlans. if this still doesn't make sense, feel free to ask...would love to help. regards, /vicky Thanks again! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63228&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
My posts on Layer 3 switching and VLAN [7:63224]
For some reason my responses are taking a REALLY long time to get to the list in relation to other people's responses, so the conversation is losing continuity. I sent an email at 8:55PM CST and I am writing this at 10:19PM CST and my 8:55 post still has not made it to the list. This is adding to the confusion. I think I had it all straight at Priscilla's posting with this history of LANs. Thanks! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63224&t=63224 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
All, I'd like to add to this something that I haven't seen in other posts yet, and that is a quick look at layer2 function. I have a Catalyst 6509 with an MSFC on it. There is only *ONE* VLAN configured on the MSFC, however, that VLAN has several secondary addresses assigned to it (I know, not a great solution, but let's not go there). If I do a "show mls entry" on my switch, it is full of entries for hosts talking to hosts on the same VLAN. My point? When a host wants to talk to a host on another subnet (VLAN or not), it ANDs the address with it's own mask, determines that the host is in fact on a different subnet, then arps (if necessary) for it's default gateway (the MSFC) and sends the packet on it's way. The 6509/MSFC receive the packet and begin the MLS cache setup process (candidate packet, timeout, etc). All this is still done inspite of the fact that the MSFC only has a single VLAN. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Stephen Hoover Sent: Monday, February 17, 2003 8:33 PM To: [EMAIL PROTECTED] Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > - > > actually it is by doing secondaries, but i would highly recommend doing > > vlans if possible. keep it clean and simple. > > > one may also configure the physical interfaces as L3 interfaces - just as > one might do on a router with several ethernet ports. Oo ok, now THAT statement leads me to believe the L3 switching IS possible without VLANs. -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63221&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
its entirely possible without vlans..majority of the cisco campus is networked with layer 3 switches and not using vlans Larry Letterman Network Engineer Cisco Systems - Original Message - From: "Stephen Hoover" To: Sent: Monday, February 17, 2003 5:32 PM Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > > - > > > actually it is by doing secondaries, but i would highly recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > one may also configure the physical interfaces as L3 interfaces - just as > > one might do on a router with several ethernet ports. > > > Oo ok, now THAT statement leads me to believe the L3 switching IS > possible without VLANs. > > > -Stephen [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63216&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
I appreciate everyone's input on this subject to help me understand this concept. As far as the newbies comment goes - I most definitely am. I'm about as green as they come. I have both my CCNA and my CCDA, but my only real experience is installing 2 T1s (at different locations) and configuring NAT for them. I have large amount of knowledge, just no experience. It has been my goal and my dream to become a serious network engineer for the last 6 years, but I just cannot seem to get a job that offers any experience. Everytime I get a "network" position, I just seemed to end up doing desktop support. When I first heard the term Layer 3 switching (some 4 years ago now) the first thing that popped into my mind was a switch that can route. I never even heard of a VLAN until a couple of years ago. The Cisco Study guide starts off talking about VLANs, and moves right into Inter-VLAN routing without ever really discussing Layer 3 switching as a seperate process. This is really where my confusion started. The book makes it sound like L3 switching is directly dependent on VLANs, and I just didn't see it - it wasn't something I was just willing to accept. Further more, the book states that VLANs allow for physical location independence, but is also says that VLANs should not cross the core - those 2 statements seem partly contradictory to me. Here is a summary of how I see VLANs now. Layer 3 switching is possible without VLANs (however the opposite is not true. Well at least not without some form of Layer 3 intervention.) VLANs simply the administration behind Layer 3 switching design. Physical location (port location) independence is ok in front of the layer 3 switch that is the the hosts gateway. Up to the hosts distribution switch. VLANs extending beyond the distribution layer switch across the core is generally not a good idea - possible, but not recommended. This is the "flat earth" design that Priscilla mentioned - VLANs that extend across the entire internetwork. Thanks! Stephen Hoover Dallas, Texas - Original Message - From: "Priscilla Oppenheimer" To: Sent: Monday, February 17, 2003 7:04 PM Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > This might help. What does the V stand for in VLAN? Virtual. VLANs are a > method for emulating Real LANs in a switched network. The original poster > seems disillusioned with VLANs. Well, I am too. :-) You can't do much with > them that you can't do with a bunch of Real LANs connected by routers. > > Better come up with a way to emulate LAN and IP subnet benefits on a > switched networks. OK, let's invent VLANs! > > But how do the VLANs talk to each other? Oh dear, we better go back to > routers. Nah, still too slow, though it will work in a pinch. I know! We > could speed them up and call them L3 switches. > > > One last rather serious comment. This is not a comment on the newbiness of > the original poster, but I must say that I think it is common for newbies to > get confused by VLANs. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63210&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
HTH, Thank you for these comments - this clears up a lot of confusion for me. To sum, just to make sure I really have this: Layer 3 switching is possible without VLANs (however the opposite is not true. Well at least not without some form of Layer 3 intervention.) VLANs simply the administration behind Layer 3 switching design. Physical location (port location) independence is ok in front of the layer 3 switch that is the the hosts gateway. Up to the hosts distribution switch. VLANs extending beyond the distribution layer switch across the core is generally not a good idea - possible, but not recommended. This is the "flat earth" design that Priscilla mentioned - VLANs that extend across the entire internetwork. Thanks! Stephen Hoover Dallas, Texas - Original Message - From: "The Long and Winding Road" To: Sent: Monday, February 17, 2003 6:00 PM Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] > I've been following this thread, and have offered a comment or two along the > way. Perhaps I should offer some thoughts here at the source. > > note that I have not read any of the exam study materials in question, so I > don't know what is or is not being stated in the courseware. I can offer > that just because it says so in the study materials doesn't mean that's the > way it is. > > comments below > > > ""Stephen Hoover"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > I am studying for the CCNP Switching exam and it covers VLANs and layer 3 > > switching moderately. It states that Cisco recommends a 1 to 1 mapping of > > VLANs to subnets. It also states that VLANs can be used to break up > > broadcast domains. > > this is a reasonable, simple approach, and thus one that appeals to my > reasonably simple mind. > > > > > > When you create different subnets, you are already breaking up broadcast > > domains, so does layer 3 switching require the use of VLANs to actually do > > the switching? > > > this is where the confusion, no doubt introduced by the marketing people, > set in. > > suppose you have a router with three ethernet interfaces, and each of these > interfaces is plugged into a different hub ( no switch ) > > hosts on each of these hubs are in the same broadcast domain ( same > collision domain too, but I digress ) hosts in each of these domains cannot > reach hosts ( or servers ) in other domians, on different hubs, without > routing. > > this would be true, even if you had all hosts on the same great big hub with > 500 ports. You could have hosts on the same hub, but having different L3 ( > IP ) addresses. communication between hosts on different subnets, even if > they are on the same hub, require the intrercession of a router. > > vlans, made possible by various 802.1 specifications, are really just a way > of expressing logical broadcast domains. > > layer 3 switching is really routing. an L3 switch has the routing function > built into it, rather than using a separate piece of equipment. > > > > > > Say for instance I have 2 hosts on the same layer 3 switch, but the two > > hosts are on 2 different IP subnets (No VLANs are defined). Host A wants > to > > talk to host B. Can the switch not look up the routing info and then know > to > > switch to that port? I am not seeing where the requirement for the VLAN > > comes into play. > > despite what others have said, you can do this. it is wasteful, in that a > host plugged into an L3 port would require 4 ip addresses because you have a > subnet with two hosts ( the PC and the port, and the net number and the > broadcast address ). whereas if you have a vlan, that vlan is a virutal port > that represents the physical ports as a single subnet to the L3 ( routing ) > function. > > > > > > If VLANs are required for layer 3 switching, is that pretty much standard > > across the industry, or that a Cisco only thing? > > > forget this L3 switch versus router distinction. it is confusing, and > misrepresentational. > > think instead in terms of how traffic moves through a network. > > think instead of a vlan as a virtual logical construct that represents one > or more ports as a single broadcast domain to a router. it doesn't matter > that the router is integrated into the switch hardware with an ASIC and > code, or is an external device. > > HTH > > > > > > Thanks! > > Stephen Hoover > > Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63208&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
""Stephen Hoover"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > - > > > actually it is by doing secondaries, but i would highly recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > one may also configure the physical interfaces as L3 interfaces - just as > > one might do on a router with several ethernet ports. > > > Oo ok, now THAT statement leads me to believe the L3 switching IS > possible without VLANs. > forgive the rant. you are not to blame. all the marketing hype is to blame. forget OSI. For L-anything. for data ( packets, frames, whatever ) to get from here to there, somethng has to happen. if I have a 75xx router with 300 ethernet ports, and I bridge all those ports, do I have an L3 switch, or a router? for data to get from here to there, it must be forwarded. I know Howard is going to jump all over my fast and loose use of the term "forward" but that is what happens. If my PC wants to send data to your PC, that data is forwarded to your PC. If your PC and mine are on the same subnet / hub / switch / vlan, it is L2 forwarding ( switching ). If the devices are on different subnets / switches . vlans / hubs then the packets are L3 forwarded ( routed ) As Priscilla has been pointing out, the issue is one of how networks work, how packets are forwarded, how data gets from here to there. An L3 device is a router is able to forward packets based on an L3 address, whether that L3 address be appletalk, IPX, or IP. an L2 device is a switch is a bridge is able to forward packets based on L2 addreses i.e. MAC address. the fact that some equipment can function as both a switch and a router ( anyone remember "brouters"? ) is irrelevant. on a 3550, a physical port ( into which you plug the ethernet patch cable ) can be stand alone physical, can be part of a vlan, thus making it distinct from ports on the same box that are not in the same vlan, or can have an IP ( L3 ) address. an SVI ( switch virtual interface ), invoked by the command "interface vlan x", is a representation of a group of ports that have been placed into a single vlan. The SVI represents those ports to the routing funtion, and behaves no differently that a router's ethernet port plugged into a hub. I'm hoping this helps clarify the concept. I believe you have been confused by the study materials you are reading, and by the mis-information that has been presented here on the list. sorry to have not taken the time to be more thorough in earlier replies. you can never go wrong studying Priscilla's posts, either. hope this is starting to make sense to you . Chuck > > -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63206&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
hi, comments in-line: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of The Long and Winding Road Sent: Monday, February 17, 2003 3:41 PM To: [EMAIL PROTECTED] Subject: Re: Does MLS (Layer 3 switching) require VLANs? [7:63147] ""Vicky Rode"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > comment in-line: > > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Monday, February 17, 2003 2:10 AM > To: [EMAIL PROTECTED] > Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > > DEar Stefen, > > you are doing a bit of confusion: > > > so does layer 3 switching require the use of VLANs to actually do > > the switching? > > It's true the contrary case: the Vlans requires L3 to be routed, or, in > other terms, to comunicate each others. The L3 switching has no sens without > VLAN > > > Say for instance I have 2 hosts on the same layer 3 switch, but the > two > hosts are on 2 different IP subnets (No VLANs are defined). > > That's not possible! if you are talking about 2 IP subnet, than: > - > actually it is by doing secondaries, but i would highly recommend doing > vlans if possible. keep it clean and simple. one may also configure the physical interfaces as L3 interfaces - just as one might do on a router with several ethernet ports. --- true enough.i would love to move to native ios provided it reaches complete feature parity w/ catos. that's all. regards, /vicky > > > > > /vicky > > > 1) you are talking about 2 subnet in 2 distinct sides of a router > 2) you are talking about 2 Vlans in one L3 switch > > > Host A wants to talk to host B. Can the switch not look up the > > routing info and then know to switch to that port? I am not seeing > where > the requirement for the VLAN comes into play. > > 1) host A and Host B are in two different VLAn: they need the L3 engine to > comunicate > 2) host A and host B are in the same Vlan but they have IP addresses (be > careful this anyway a mistake!) who belongs to different VLAN: A can't > comunicate with B because A doesn't know the MAC of B ... A can have > knoledge of the MAC's of > a) the hosts in the same subnet > b) the gateway of the A's subnet > and B's MAC doesn't match either of the a and b case. > > Hope this halp you > > Greetings > > Luca Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63205&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
> > - > > actually it is by doing secondaries, but i would highly recommend doing > > vlans if possible. keep it clean and simple. > > > one may also configure the physical interfaces as L3 interfaces - just as > one might do on a router with several ethernet ports. Oo ok, now THAT statement leads me to believe the L3 switching IS possible without VLANs. -Stephen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63204&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
good for you, Cil. This discussion was ( and still is, to judge from my in-box ) filled with misdirection and poor information. Cisco and all the other vendors are absolutely to blame for this. a router is a function, not a device so is a switch. what does it matter where the function resides, or how it is accomplished? -- TANSTAAFL "there ain't no such thing as a free lunch" ""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > This might help. What does the V stand for in VLAN? Virtual. VLANs are a > method for emulating Real LANs in a switched network. The original poster > seems disillusioned with VLANs. Well, I am too. :-) You can't do much with > them that you can't do with a bunch of Real LANs connected by routers. > > First we had hubs and bridges and routers. Then switches came out. They were > cheaper and faster than routers, so everyone jumped on the bandwagon and > started designing huge flat networks with mostly switches and maybe one > router to get out to the rest of the world. > > Ah, but there was a problem! A L2 switch forwards broadcasts out all ports. > And this was in the mid-1990s when PC CPUs were slow as molasses and got > bogged down by broadcasts and multicasts. Dreadful protocols like SAP and > RTMP and NetBIOS were rampant! Something had to be done. > > So, hu, should we go back to designing our networks with routers, which > don't forward broadcasts? Nah, still too expensive. > > Better come up with a way to emulate LAN and IP subnet benefits on a > switched networks. OK, let's invent VLANs! > > But how do the VLANs talk to each other? Oh dear, we better go back to > routers. Nah, still too slow, though it will work in a pinch. I know! We > could speed them up and call them L3 switches. > > > One last rather serious comment. This is not a comment on the newbiness of > the original poster, but I must say that I think it is common for newbies to > get confused by VLANs. > > Cisco teaches VLANs without ever teaching basic networking 101. People can't > understand VLANs unless they first understand a lot more about protocol > behavior and traffic flow. VLANs are really an advanced topic and shouldn't > be covered so early on in the Cisco test progression. Either that or CCNA > should be beefed up to teach something useful, if you ask me, which they > didn't. > > Priscilla > > > The Long and Winding Road wrote: > > > > I've been following this thread, and have offered a comment or > > two along the > > way. Perhaps I should offer some thoughts here at the source. > > > > note that I have not read any of the exam study materials in > > question, so I > > don't know what is or is not being stated in the courseware. I > > can offer > > that just because it says so in the study materials doesn't > > mean that's the > > way it is. > > > > comments below > > > > > > ""Stephen Hoover"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > I am studying for the CCNP Switching exam and it covers VLANs > > and layer 3 > > > switching moderately. It states that Cisco recommends a 1 to > > 1 mapping of > > > VLANs to subnets. It also states that VLANs can be used to > > break up > > > broadcast domains. > > > > this is a reasonable, simple approach, and thus one that > > appeals to my > > reasonably simple mind. > > > > > > > > > > When you create different subnets, you are already breaking > > up broadcast > > > domains, so does layer 3 switching require the use of VLANs > > to actually do > > > the switching? > > > > > > this is where the confusion, no doubt introduced by the > > marketing people, > > set in. > > > > suppose you have a router with three ethernet interfaces, and > > each of these > > interfaces is plugged into a different hub ( no switch ) > > > > hosts on each of these hubs are in the same broadcast domain ( > > same > > collision domain too, but I digress ) hosts in each of these > > domains cannot > > reach hosts ( or servers ) in other domians, on different hubs, > > without > > routing. > > > > this would be true, even if you had all hosts on the same great > > big hub with > > 500 ports. You could have hosts on the same hub, but having > > different L3 ( > > IP ) addresses. communication between hosts on different > > subnets, even if > > they are on the same hub, r
Re: Does MLS (Layer 3 switching) require VLANs? YES [7:63147]
comments inline. --- Jens Neelsen wrote: > Hi, > > a layer3 switch (e.g.3550-EMI) does not have layer3 > interfaces. > All interfaces (Fastethernet and GigabitEthernet) > are layer2 > interfaces. They can not have IP addresses. On the 3550, you can have IP addresses on the actual interface if you do a 'no switchport' command thus making it not a switch port. > The VLANs are the (virtual) interfaces to the > routing engine (=layer3 switch). You can group ports together in the same VLAN by making them in the same access VLAN with the switchport command. Then you can optionally create a SVI for the VLANs you want to route on this switch. It's akin to a BVI on the routers. I don't know why they call it a SVI - just more acronyms. A switch is a multiport bridge. And same for "fallback-bridging" which is regular "bridge" commands that have been used on routers for a long time. > Layer2 interfaces are grouped into different VLANs > and the > Layer3 switch (=Router) enables the communications > between these VLANs. > > A Router has to have different IP subnets on each > interface. > Because the VLANs are the interfaces to the router, > you need > different subnets on each VLAN. See above. > With secondary IP adresses you can have more than > one IP subnet > on a VLAN. But as with router interfaces the subnets > of the > VLANs cannot overlap. > > A 5000 switch with RSM works in the same way. This > is covered in > the Cisco BCMSN training course. > > With kind regards > Jens Neelsen > > --- Stephen Hoover wrote: > > > > Say for instance I have 2 hosts on the same > layer 3 > > switch, but the > > > two > > > hosts are on 2 different IP subnets (No VLANs > are defined). > > > > > > That's not possible! if you are talking about 2 > IP subnet, > > than: > > > - > > > actually it is by doing secondaries, but i would > highly > > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > > > > Vicki, > > > > You mention the use of secondary IP's. On a L3 > switch (a > > switch with the > > router engine in it) is it not possible to define > Ethernet sub > > interfaces > > instead of using secondary IPs - without VLANs > defined? > > > > > > I'm sorry to be so thick, I'm just not getting > it. If a L3 > > switch (with > > a routing module/engine in it) is essentially a > wire speed > > router, then the > > VLAN just seems like an additional identifier on > top of the L3 > > address - and > > doesn't really serve any purpose. In my previous > example, 2 > > hosts on the > > same L3 switch, but on 2 different IP subnets - > wouldn't a > > defined Ethernet > > subinterface be each clients respective gateway, > and thus > > normal L3 routing > > would occur, just at switch speeds > > > > > > Thanks again! > > > > Stephen Hoover > > Dallas, Texas > [EMAIL PROTECTED] __ Do you Yahoo!? Yahoo! Shopping - Send Flowers for Valentine's Day http://shopping.yahoo.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63197&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
This might help. What does the V stand for in VLAN? Virtual. VLANs are a method for emulating Real LANs in a switched network. The original poster seems disillusioned with VLANs. Well, I am too. :-) You can't do much with them that you can't do with a bunch of Real LANs connected by routers. First we had hubs and bridges and routers. Then switches came out. They were cheaper and faster than routers, so everyone jumped on the bandwagon and started designing huge flat networks with mostly switches and maybe one router to get out to the rest of the world. Ah, but there was a problem! A L2 switch forwards broadcasts out all ports. And this was in the mid-1990s when PC CPUs were slow as molasses and got bogged down by broadcasts and multicasts. Dreadful protocols like SAP and RTMP and NetBIOS were rampant! Something had to be done. So, hu, should we go back to designing our networks with routers, which don't forward broadcasts? Nah, still too expensive. Better come up with a way to emulate LAN and IP subnet benefits on a switched networks. OK, let's invent VLANs! But how do the VLANs talk to each other? Oh dear, we better go back to routers. Nah, still too slow, though it will work in a pinch. I know! We could speed them up and call them L3 switches. One last rather serious comment. This is not a comment on the newbiness of the original poster, but I must say that I think it is common for newbies to get confused by VLANs. Cisco teaches VLANs without ever teaching basic networking 101. People can't understand VLANs unless they first understand a lot more about protocol behavior and traffic flow. VLANs are really an advanced topic and shouldn't be covered so early on in the Cisco test progression. Either that or CCNA should be beefed up to teach something useful, if you ask me, which they didn't. Priscilla The Long and Winding Road wrote: > > I've been following this thread, and have offered a comment or > two along the > way. Perhaps I should offer some thoughts here at the source. > > note that I have not read any of the exam study materials in > question, so I > don't know what is or is not being stated in the courseware. I > can offer > that just because it says so in the study materials doesn't > mean that's the > way it is. > > comments below > > > ""Stephen Hoover"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > I am studying for the CCNP Switching exam and it covers VLANs > and layer 3 > > switching moderately. It states that Cisco recommends a 1 to > 1 mapping of > > VLANs to subnets. It also states that VLANs can be used to > break up > > broadcast domains. > > this is a reasonable, simple approach, and thus one that > appeals to my > reasonably simple mind. > > > > > > When you create different subnets, you are already breaking > up broadcast > > domains, so does layer 3 switching require the use of VLANs > to actually do > > the switching? > > > this is where the confusion, no doubt introduced by the > marketing people, > set in. > > suppose you have a router with three ethernet interfaces, and > each of these > interfaces is plugged into a different hub ( no switch ) > > hosts on each of these hubs are in the same broadcast domain ( > same > collision domain too, but I digress ) hosts in each of these > domains cannot > reach hosts ( or servers ) in other domians, on different hubs, > without > routing. > > this would be true, even if you had all hosts on the same great > big hub with > 500 ports. You could have hosts on the same hub, but having > different L3 ( > IP ) addresses. communication between hosts on different > subnets, even if > they are on the same hub, require the intrercession of a router. > > vlans, made possible by various 802.1 specifications, are > really just a way > of expressing logical broadcast domains. > > layer 3 switching is really routing. an L3 switch has the > routing function > built into it, rather than using a separate piece of equipment. > > > > > > Say for instance I have 2 hosts on the same layer 3 switch, > but the two > > hosts are on 2 different IP subnets (No VLANs are defined). > Host A wants > to > > talk to host B. Can the switch not look up the routing info > and then know > to > > switch to that port? I am not seeing where the requirement > for the VLAN > > comes into play. > > despite what others have said, you can do this. it is wasteful, > in that a > host plugged into an L3 port would require 4 ip addresses > because you have a > subnet with two hosts ( the PC and the port, and the net number > and t
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
I've been following this thread, and have offered a comment or two along the way. Perhaps I should offer some thoughts here at the source. note that I have not read any of the exam study materials in question, so I don't know what is or is not being stated in the courseware. I can offer that just because it says so in the study materials doesn't mean that's the way it is. comments below ""Stephen Hoover"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I am studying for the CCNP Switching exam and it covers VLANs and layer 3 > switching moderately. It states that Cisco recommends a 1 to 1 mapping of > VLANs to subnets. It also states that VLANs can be used to break up > broadcast domains. this is a reasonable, simple approach, and thus one that appeals to my reasonably simple mind. > > When you create different subnets, you are already breaking up broadcast > domains, so does layer 3 switching require the use of VLANs to actually do > the switching? this is where the confusion, no doubt introduced by the marketing people, set in. suppose you have a router with three ethernet interfaces, and each of these interfaces is plugged into a different hub ( no switch ) hosts on each of these hubs are in the same broadcast domain ( same collision domain too, but I digress ) hosts in each of these domains cannot reach hosts ( or servers ) in other domians, on different hubs, without routing. this would be true, even if you had all hosts on the same great big hub with 500 ports. You could have hosts on the same hub, but having different L3 ( IP ) addresses. communication between hosts on different subnets, even if they are on the same hub, require the intrercession of a router. vlans, made possible by various 802.1 specifications, are really just a way of expressing logical broadcast domains. layer 3 switching is really routing. an L3 switch has the routing function built into it, rather than using a separate piece of equipment. > > Say for instance I have 2 hosts on the same layer 3 switch, but the two > hosts are on 2 different IP subnets (No VLANs are defined). Host A wants to > talk to host B. Can the switch not look up the routing info and then know to > switch to that port? I am not seeing where the requirement for the VLAN > comes into play. despite what others have said, you can do this. it is wasteful, in that a host plugged into an L3 port would require 4 ip addresses because you have a subnet with two hosts ( the PC and the port, and the net number and the broadcast address ). whereas if you have a vlan, that vlan is a virutal port that represents the physical ports as a single subnet to the L3 ( routing ) function. > > If VLANs are required for layer 3 switching, is that pretty much standard > across the industry, or that a Cisco only thing? forget this L3 switch versus router distinction. it is confusing, and misrepresentational. think instead in terms of how traffic moves through a network. think instead of a vlan as a virtual logical construct that represents one or more ports as a single broadcast domain to a router. it doesn't matter that the router is integrated into the switch hardware with an ASIC and code, or is an external device. HTH > > Thanks! > Stephen Hoover > Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63190&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? YES [7:63147]
Jens, MY 3550-EMI certainly can have layer 3 interfaces. All you need to do is to enter the command "no switchport" on the interface. Check out this link: http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12112cea/3550cr/cl i2.htm#xtocid104 I quote: switchport Use the switchport interface configuration command with no keywords to put an interface that is in Layer 3 mode into Layer 2 mode for Layer 2 configuration. Use the no form of this command to put an interface in Layer 3 mode. switchport no switchport Use the no switchport command (without parameters) to set the interface to the routed-interface status and to erase all Layer 2 configurations. You must use this command before assigning an IP address to a routed port. -Bob Sinclair CCIE #10427, MCSE Senior Network Engineer Networking For Future, Inc. www.nffinc.com - Original Message - From: "Jens Neelsen" To: Sent: Monday, February 17, 2003 3:28 PM Subject: Re: Does MLS (Layer 3 switching) require VLANs? YES [7:63147] > Hi, > > a layer3 switch (e.g.3550-EMI) does not have layer3 interfaces. > All interfaces (Fastethernet and GigabitEthernet) are layer2 > interfaces. They can not have IP addresses. > > The VLANs are the (virtual) interfaces to the routing engine > (=layer3 switch). > > Layer2 interfaces are grouped into different VLANs and the > Layer3 switch (=Router) enables the communications between these > VLANs. > > A Router has to have different IP subnets on each interface. > Because the VLANs are the interfaces to the router, you need > different subnets on each VLAN. > > With secondary IP adresses you can have more than one IP subnet > on a VLAN. But as with router interfaces the subnets of the > VLANs cannot overlap. > > A 5000 switch with RSM works in the same way. This is covered in > the Cisco BCMSN training course. > > With kind regards > Jens Neelsen > > --- Stephen Hoover wrote: > > > > Say for instance I have 2 hosts on the same layer 3 > > switch, but the > > > two > > > hosts are on 2 different IP subnets (No VLANs are defined). > > > > > > That's not possible! if you are talking about 2 IP subnet, > > than: > > > - > > > actually it is by doing secondaries, but i would highly > > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > > > > Vicki, > > > > You mention the use of secondary IP's. On a L3 switch (a > > switch with the > > router engine in it) is it not possible to define Ethernet sub > > interfaces > > instead of using secondary IPs - without VLANs defined? > > > > > > I'm sorry to be so thick, I'm just not getting it. If a L3 > > switch (with > > a routing module/engine in it) is essentially a wire speed > > router, then the > > VLAN just seems like an additional identifier on top of the L3 > > address - and > > doesn't really serve any purpose. In my previous example, 2 > > hosts on the > > same L3 switch, but on 2 different IP subnets - wouldn't a > > defined Ethernet > > subinterface be each clients respective gateway, and thus > > normal L3 routing > > would occur, just at switch speeds > > > > > > Thanks again! > > > > Stephen Hoover > > Dallas, Texas > [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63189&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
""Vicky Rode"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > comment in-line: > > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Monday, February 17, 2003 2:10 AM > To: [EMAIL PROTECTED] > Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] > > > DEar Stefen, > > you are doing a bit of confusion: > > > so does layer 3 switching require the use of VLANs to actually do > > the switching? > > It's true the contrary case: the Vlans requires L3 to be routed, or, in > other terms, to comunicate each others. The L3 switching has no sens without > VLAN > > > Say for instance I have 2 hosts on the same layer 3 switch, but the > two > hosts are on 2 different IP subnets (No VLANs are defined). > > That's not possible! if you are talking about 2 IP subnet, than: > - > actually it is by doing secondaries, but i would highly recommend doing > vlans if possible. keep it clean and simple. one may also configure the physical interfaces as L3 interfaces - just as one might do on a router with several ethernet ports. > > > > > /vicky > > > 1) you are talking about 2 subnet in 2 distinct sides of a router > 2) you are talking about 2 Vlans in one L3 switch > > > Host A wants to talk to host B. Can the switch not look up the > > routing info and then know to switch to that port? I am not seeing > where > the requirement for the VLAN comes into play. > > 1) host A and Host B are in two different VLAn: they need the L3 engine to > comunicate > 2) host A and host B are in the same Vlan but they have IP addresses (be > careful this anyway a mistake!) who belongs to different VLAN: A can't > comunicate with B because A doesn't know the MAC of B ... A can have > knoledge of the MAC's of > a) the hosts in the same subnet > b) the gateway of the A's subnet > and B's MAC doesn't match either of the a and b case. > > Hope this halp you > > Greetings > > Luca Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63186&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? YES [7:63147]
""Jens Neelsen"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi, > > a layer3 switch (e.g.3550-EMI) does not have layer3 interfaces. > All interfaces (Fastethernet and GigabitEthernet) are layer2 > interfaces. They can not have IP addresses. gentle correction. by entering the "no switchport" command, one removes the particlar interface from the "L2" domain and into the L3 domain. At this point one can indeed enter IP address onto the physical inerfaces. I think you may be getting too carried away with L2 versus L3. A physical port exists in multiple layers of the OSI model, if you want to talk in terms of OSI. There is the physical port. There is whatever that physical port talks to and how. For example, an ethernet port has physical and mac layer characteristics. otherwise, how would it communicate with other devices on the wire? Add an IP address, and that port is now "L3" as well. A router with an ethernet interface plugged into a switch operates at all three "layers" of OSI. > > The VLANs are the (virtual) interfaces to the routing engine > (=layer3 switch). yes. good way of putting it. > > Layer2 interfaces are grouped into different VLANs and the > Layer3 switch (=Router) enables the communications between these > VLANs. one can also bridge between vlans, at least in the 3550 world. fallback bridging. > > A Router has to have different IP subnets on each interface. > Because the VLANs are the interfaces to the router, you need > different subnets on each VLAN. if you have subnet based vlans. remember that you can also have ip addressing on different ports, although, as you say, these all have to be on different subnets. unless you are etherchanneling, but that's a different story. but to get back to point here, what is the difference between a physical port configured with an IP address and a physical port assigned to a vlan, with the vlan having an ip address? > > With secondary IP adresses you can have more than one IP subnet > on a VLAN. But as with router interfaces the subnets of the > VLANs cannot overlap. > > A 5000 switch with RSM works in the same way. This is covered in > the Cisco BCMSN training course. > > With kind regards > Jens Neelsen > > --- Stephen Hoover wrote: > > > > Say for instance I have 2 hosts on the same layer 3 > > switch, but the > > > two > > > hosts are on 2 different IP subnets (No VLANs are defined). > > > > > > That's not possible! if you are talking about 2 IP subnet, > > than: > > > - > > > actually it is by doing secondaries, but i would highly > > recommend doing > > > vlans if possible. keep it clean and simple. > > > > > > > > > Vicki, > > > > You mention the use of secondary IP's. On a L3 switch (a > > switch with the > > router engine in it) is it not possible to define Ethernet sub > > interfaces > > instead of using secondary IPs - without VLANs defined? > > > > > > I'm sorry to be so thick, I'm just not getting it. If a L3 > > switch (with > > a routing module/engine in it) is essentially a wire speed > > router, then the > > VLAN just seems like an additional identifier on top of the L3 > > address - and > > doesn't really serve any purpose. In my previous example, 2 > > hosts on the > > same L3 switch, but on 2 different IP subnets - wouldn't a > > defined Ethernet > > subinterface be each clients respective gateway, and thus > > normal L3 routing > > would occur, just at switch speeds > > > > > > Thanks again! > > > > Stephen Hoover > > Dallas, Texas > [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63185&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? YES [7:63147]
Hi, a layer3 switch (e.g.3550-EMI) does not have layer3 interfaces. All interfaces (Fastethernet and GigabitEthernet) are layer2 interfaces. They can not have IP addresses. The VLANs are the (virtual) interfaces to the routing engine (=layer3 switch). Layer2 interfaces are grouped into different VLANs and the Layer3 switch (=Router) enables the communications between these VLANs. A Router has to have different IP subnets on each interface. Because the VLANs are the interfaces to the router, you need different subnets on each VLAN. With secondary IP adresses you can have more than one IP subnet on a VLAN. But as with router interfaces the subnets of the VLANs cannot overlap. A 5000 switch with RSM works in the same way. This is covered in the Cisco BCMSN training course. With kind regards Jens Neelsen --- Stephen Hoover wrote: > > > Say for instance I have 2 hosts on the same layer 3 > switch, but the > > two > > hosts are on 2 different IP subnets (No VLANs are defined). > > > > That's not possible! if you are talking about 2 IP subnet, > than: > > - > > actually it is by doing secondaries, but i would highly > recommend doing > > vlans if possible. keep it clean and simple. > > > > > Vicki, > > You mention the use of secondary IP's. On a L3 switch (a > switch with the > router engine in it) is it not possible to define Ethernet sub > interfaces > instead of using secondary IPs - without VLANs defined? > > > I'm sorry to be so thick, I'm just not getting it. If a L3 > switch (with > a routing module/engine in it) is essentially a wire speed > router, then the > VLAN just seems like an additional identifier on top of the L3 > address - and > doesn't really serve any purpose. In my previous example, 2 > hosts on the > same L3 switch, but on 2 different IP subnets - wouldn't a > defined Ethernet > subinterface be each clients respective gateway, and thus > normal L3 routing > would occur, just at switch speeds > > > Thanks again! > > Stephen Hoover > Dallas, Texas [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63174&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
> > Say for instance I have 2 hosts on the same layer 3 switch, but the > two > hosts are on 2 different IP subnets (No VLANs are defined). > > That's not possible! if you are talking about 2 IP subnet, than: > - > actually it is by doing secondaries, but i would highly recommend doing > vlans if possible. keep it clean and simple. > Vicki, You mention the use of secondary IP's. On a L3 switch (a switch with the router engine in it) is it not possible to define Ethernet sub interfaces instead of using secondary IPs - without VLANs defined? I'm sorry to be so thick, I'm just not getting it. If a L3 switch (with a routing module/engine in it) is essentially a wire speed router, then the VLAN just seems like an additional identifier on top of the L3 address - and doesn't really serve any purpose. In my previous example, 2 hosts on the same L3 switch, but on 2 different IP subnets - wouldn't a defined Ethernet subinterface be each clients respective gateway, and thus normal L3 routing would occur, just at switch speeds Thanks again! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63171&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Does MLS (Layer 3 switching) require VLANs? [7:63147]
> > so does layer 3 switching require the use of VLANs to actually do > > the switching? > > It's true the contrary case: the Vlans requires L3 to be routed, or, in > other terms, to comunicate each others. The L3 switching has no sens without > VLAN > Right, I understand that inter-VLAN routing requires L3 switching - but is the opposite also true? Does L3 switching require VLANs to be defined? If that is the case, then it would lead me to believe that L3 switching is based on VLAN info and not on the IP address, but I don't think that is correct. Thanks for the help! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63169&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
comment in-line: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] Sent: Monday, February 17, 2003 2:10 AM To: [EMAIL PROTECTED] Subject: RE: Does MLS (Layer 3 switching) require VLANs? [7:63147] DEar Stefen, you are doing a bit of confusion: > so does layer 3 switching require the use of VLANs to actually do > the switching? It's true the contrary case: the Vlans requires L3 to be routed, or, in other terms, to comunicate each others. The L3 switching has no sens without VLAN > Say for instance I have 2 hosts on the same layer 3 switch, but the > two hosts are on 2 different IP subnets (No VLANs are defined). That's not possible! if you are talking about 2 IP subnet, than: - actually it is by doing secondaries, but i would highly recommend doing vlans if possible. keep it clean and simple. /vicky 1) you are talking about 2 subnet in 2 distinct sides of a router 2) you are talking about 2 Vlans in one L3 switch > Host A wants to talk to host B. Can the switch not look up the > routing info and then know to switch to that port? I am not seeing > where the requirement for the VLAN comes into play. 1) host A and Host B are in two different VLAn: they need the L3 engine to comunicate 2) host A and host B are in the same Vlan but they have IP addresses (be careful this anyway a mistake!) who belongs to different VLAN: A can't comunicate with B because A doesn't know the MAC of B ... A can have knoledge of the MAC's of a) the hosts in the same subnet b) the gateway of the A's subnet and B's MAC doesn't match either of the a and b case. Hope this halp you Greetings Luca Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63160&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Does MLS (Layer 3 switching) require VLANs? [7:63147]
DEar Stefen, you are doing a bit of confusion: > so does layer 3 switching require the use of VLANs to actually do > the switching? It's true the contrary case: the Vlans requires L3 to be routed, or, in other terms, to comunicate each others. The L3 switching has no sens without VLAN > Say for instance I have 2 hosts on the same layer 3 switch, but the > two hosts are on 2 different IP subnets (No VLANs are defined). That's not possible! if you are talking about 2 IP subnet, than: 1) you are talking about 2 subnet in 2 distinct sides of a router 2) you are talking about 2 Vlans in one L3 switch > Host A wants to talk to host B. Can the switch not look up the > routing info and then know to switch to that port? I am not seeing > where the requirement for the VLAN comes into play. 1) host A and Host B are in two different VLAn: they need the L3 engine to comunicate 2) host A and host B are in the same Vlan but they have IP addresses (be careful this anyway a mistake!) who belongs to different VLAN: A can't comunicate with B because A doesn't know the MAC of B ... A can have knoledge of the MAC's of a) the hosts in the same subnet b) the gateway of the A's subnet and B's MAC doesn't match either of the a and b case. Hope this halp you Greetings Luca Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63153&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Does MLS (Layer 3 switching) require VLANs? [7:63147]
I am studying for the CCNP Switching exam and it covers VLANs and layer 3 switching moderately. It states that Cisco recommends a 1 to 1 mapping of VLANs to subnets. It also states that VLANs can be used to break up broadcast domains. When you create different subnets, you are already breaking up broadcast domains, so does layer 3 switching require the use of VLANs to actually do the switching? Say for instance I have 2 hosts on the same layer 3 switch, but the two hosts are on 2 different IP subnets (No VLANs are defined). Host A wants to talk to host B. Can the switch not look up the routing info and then know to switch to that port? I am not seeing where the requirement for the VLAN comes into play. If VLANs are required for layer 3 switching, is that pretty much standard across the industry, or that a Cisco only thing? Thanks! Stephen Hoover Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63147&t=63147 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Question about fast switching and layer 3 switching [7:14044]
Hi, Dovelet Fast switching is implemented in software(IOS). It is a in-memory cache. Layer-3 switching normally is implemented in hardware, such as hardware cache or ASIC chip. Michael "dovelet" wrote in message ... >Hi all, > >I have a question and I hope someone can help me. As I know, Cisco router >support several switching method, e.g. process switching, fast switching >etc. In some document, it state that fast switching is when the 1st packet >goes into a router, it will go through the routing process, the other >packets with the same source and destination address will go through the >switching process. As I know, the layer 3 switching router is doing the same >job. Then, what is the different between a layer3 switching router and a >router in fast switching? > >Regards, >dovelet Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=14044&t=14044 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Question about fast switching and layer 3 switching [7:13962]
Hi, what you said is almost correct ... Proccess/Fast/Distributed/Packet switching are all layer 2 functions.. >From the CCO Fast switching allows higher throughput by switching a packet using a cache created by the initial packet sent to a particular destination. "this is all done at layer 2" Destination addresses are stored in the high-speed (switching)cache to expedite forwarding. Routers offer better packet-transfer performance when fast switching is enabled. Fast switching is enabled by default on all interfaces that support fast switching. layer 3 switching differs from this by having the first packet sent to the router (which routes the packet to the correct outgoing port ..this is a more efficent way of finding destinations than switching ,...switching envolves looking at a singular table or flooding -leaveing out CEF on purpose-) it then stores this info in the cache and all following/Same destination packets are switched using info in the cache... i have read somewhere that is 4-9 times faster to switch a packet than to route one so this gives us an increase in throughput via "intelligent switching"-my own term please don`t quote me on the 4-9 times bit ...but it IS defenatly faster to switch .. HTH steve >From: "dovelet" >Reply-To: "dovelet" >To: [EMAIL PROTECTED] >Subject: Question about fast switching and layer 3 switching [7:13941] >Date: Fri, 27 Jul 2001 06:08:46 -0400 > >Hi all, > >I have a question and I hope someone can help me. As I know, Cisco router >support several switching method, e.g. process switching, fast switching >etc. In some document, it state that fast switching is when the 1st packet >goes into a router, it will go through the routing process, the other >packets with the same source and destination address will go through the >switching process. As I know, the layer 3 switching router is doing the >same >job. Then, what is the different between a layer3 switching router and a >router in fast switching? > >Regards, >dovelet _ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=13962&t=13962 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Question about fast switching and layer 3 switching [7:13941]
Hi all, I have a question and I hope someone can help me. As I know, Cisco router support several switching method, e.g. process switching, fast switching etc. In some document, it state that fast switching is when the 1st packet goes into a router, it will go through the routing process, the other packets with the same source and destination address will go through the switching process. As I know, the layer 3 switching router is doing the same job. Then, what is the different between a layer3 switching router and a router in fast switching? Regards, dovelet Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=13941&t=13941 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6144]
Rik, Ek! Yep I went off on one there. Mouth into overdrive - brain in neutral. I love that embarrassing feeling when you've lost the plot and not realised until it's public viewing material. I think users of a certain age should be provided with a "Delete my drivel" facility, to compensate for senility. Cheers, Gaz ""Rik Guyler"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > I think that what you have described is "multi-layer" switching. > > As Howard has mentioned in past posts, L3S is simply a marketing term as is > wire-speed switching. Layer 3 Switching is simply a line card, typically in > a chassis-based system, that can make routing decisions (layer 3) using > hardware-based technology (layer 2). By not relying on the fundamentally > slow software decision making, this process greatly enhances the speed at > which the decisions are made. > > There are other types of L3S devices, such as a 2948G-L3. This switch uses > ASICs to make routing decisions within hardware. When you purchase one of > these beasts, you basically have a 48-port gigabit router! > > Inter-VLAN routing is just routing. Basically, it can be performed with any > routing-capable device so long as you have the appropriate interfaces. The > difference between Inter-VLAn routing and legacy routing really has nothing > to do with routing at all. The real difference is how the LANs have been > broken out: either Layer 2 (VLANs) or Layer 3 (IP subnetting). > > If you know something about routing, then you know something about > Inter-VLAN routing. Read up on VLANs (I suggest the Kenndy Clark CCIE > switching book) and all will become clear. > > Rik > > -Original Message- > From: Gareth Hinton [mailto:[EMAIL PROTECTED]] > Sent: Monday, May 28, 2001 6:09 AM > To: [EMAIL PROTECTED] > Subject: Re: What do "interVLAN routing "and" Layer 3 switching " mean > [7:6104] > > > Hi Frank, > > I think the best description for Layer 3 Switching is "Route once - Switch > many". > The first time a packet in a particular "flow" passes through, a routing > function will be used (on a different card, or even in a different device). > But to speed up the processing of any further packets in that flow, a cache > is created in the switch to remember this flow. The next time a packet comes > through which matches this flow it will be switched without using the router > functionality, therefore speeding things up. > The definition of a flow can differ depending on configuration. For > instance, normally a flow may be any packet to a particular destination, but > if , for example, an extended access list is configured, the criteria for > the flow may tighten up i.e. to be considered part of a flow, the source and > destination are compared. > Inter-VLAN routing means a packet gets routed every time. > > Regards, > > Gaz > > > > > ""frank"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > What does the following mean ?it's cut from a description of WS-X4232-L3 > on > > cisco website. > > > > > > The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN > > routing for the Catalyst 4000 family switch and provides Layer 3 switching > > between the Gigabit Ethernet interfaces. > > > > "John Hardman" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hi > > > > > > OK I'll bite... > > > > > > Yes there is a difference. It gets a little convoluted, but there is a > > > difference. > > > > > > L3 switching: Think of a L3 switch as a multi port router that operates > at > > > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet > > > router. So L3 switching is routing traffic at wire speeds. You could use > > one > > > of these to route between VLANs, or route between networks. > > > > > > Inter-VLAN routing: This is a technique, technology that is only used to > > > route traffic from one VLAN to other VLAN(s). It generally takes place > at > > > wire speeds inside a Cat switch with a L3 switch option, but is often > see > > > with routers that do not work at wire speeds. > > > > > > So the bottom line... think of a L3 switch as a device, and Inter-VLAN > > > routing as a technology. > > > > > > HTH > > > -- > > > John Hardman CCNP MCSE > > > > > > > > > ""frank"" wrote in message &g
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6130]
Something about saying cisco is "new" to L3 bothers me :) Switching in hardware based on IP headers maybe, but layer 3? I think they've proven themselves there. Pete *** REPLY SEPARATOR *** On 5/28/2001 at 1:14 PM John Hardman wrote: >Hi > >It means that the 4003 and 4006 has a L3 module that can provide Inter-VLAN >routing. It might be limited to only provide Inter-VLAN routing on the FE >ports and have full L3 function on the GE ports. > >Keep in mind that Cisco is still new to L3 and as such they have not fully >implemented it on all platforms, e.g. the 2948G-L3 is not capable of doing >full ACLs on all ports, just the GE ports, or at least in the last IOS I >used on one. > >-- >John Hardman CCNP MCSE > > >""frank"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> What does the following mean ?it's cut from a description of WS-X4232-L3 >on >> cisco website. >> >> >> The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN >> routing for the Catalyst 4000 family switch and provides Layer 3 >switching >> between the Gigabit Ethernet interfaces. >> >> "John Hardman" wrote in message >> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> > Hi >> > >> > OK I'll bite... >> > >> > Yes there is a difference. It gets a little convoluted, but there is a >> > difference. >> > >> > L3 switching: Think of a L3 switch as a multi port router that operates >at >> > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet >> > router. So L3 switching is routing traffic at wire speeds. You could >use >> one >> > of these to route between VLANs, or route between networks. >> > >> > Inter-VLAN routing: This is a technique, technology that is only used >to >> > route traffic from one VLAN to other VLAN(s). It generally takes place >at >> > wire speeds inside a Cat switch with a L3 switch option, but is often >see >> > with routers that do not work at wire speeds. >> > >> > So the bottom line... think of a L3 switch as a device, and Inter-VLAN >> > routing as a technology. >> > >> > HTH >> > -- >> > John Hardman CCNP MCSE >> > >> > >> > ""frank"" wrote in message >> > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> > > Any difference? >> > > >> > > "frank" wrote in message >> > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> > > > Thanks, >> > > > >> > > > >> > > > Frank >> > > > FAQ, list archives, and subscription info: >> > > http://www.groupstudy.com/list/cisco.html >> > > > Report misconduct and Nondisclosure violations to >[EMAIL PROTECTED] >> > > FAQ, list archives, and subscription info: >> > http://www.groupstudy.com/list/cisco.html >> > > Report misconduct and Nondisclosure violations to >[EMAIL PROTECTED] >> > FAQ, list archives, and subscription info: >> http://www.groupstudy.com/list/cisco.html >> > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] >> FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6130&t=6130 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6126]
Hi It means that the 4003 and 4006 has a L3 module that can provide Inter-VLAN routing. It might be limited to only provide Inter-VLAN routing on the FE ports and have full L3 function on the GE ports. Keep in mind that Cisco is still new to L3 and as such they have not fully implemented it on all platforms, e.g. the 2948G-L3 is not capable of doing full ACLs on all ports, just the GE ports, or at least in the last IOS I used on one. -- John Hardman CCNP MCSE ""frank"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > What does the following mean ?it's cut from a description of WS-X4232-L3 on > cisco website. > > > The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN > routing for the Catalyst 4000 family switch and provides Layer 3 switching > between the Gigabit Ethernet interfaces. > > "John Hardman" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi > > > > OK I'll bite... > > > > Yes there is a difference. It gets a little convoluted, but there is a > > difference. > > > > L3 switching: Think of a L3 switch as a multi port router that operates at > > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet > > router. So L3 switching is routing traffic at wire speeds. You could use > one > > of these to route between VLANs, or route between networks. > > > > Inter-VLAN routing: This is a technique, technology that is only used to > > route traffic from one VLAN to other VLAN(s). It generally takes place at > > wire speeds inside a Cat switch with a L3 switch option, but is often see > > with routers that do not work at wire speeds. > > > > So the bottom line... think of a L3 switch as a device, and Inter-VLAN > > routing as a technology. > > > > HTH > > -- > > John Hardman CCNP MCSE > > > > > > ""frank"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Any difference? > > > > > > "frank" wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Thanks, > > > > > > > > > > > > Frank > > > > FAQ, list archives, and subscription info: > > > http://www.groupstudy.com/list/cisco.html > > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6126&t=6126 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6125]
>Hi > >OK I'll bite... > >Yes there is a difference. It gets a little convoluted, but there is a >difference. > >L3 switching: Think of a L3 switch as a multi port router that operates at >wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet >router. So L3 switching is routing traffic at wire speeds. You could use one >of these to route between VLANs, or route between networks. > >Inter-VLAN routing: This is a technique, technology that is only used to >route traffic from one VLAN to other VLAN(s). It generally takes place at >wire speeds inside a Cat switch with a L3 switch option, but is often see >with routers that do not work at wire speeds. > >So the bottom line... think of a L3 switch as a device, and Inter-VLAN >routing as a technology. > >HTH >-- >John Hardman CCNP MCSE Your bottom line is a nice way to distinguish, one I don't usually use but one that makes sense. My biggest problem with some of these terms is that they really don't have any technical meaning. They may have product family connotations, but they are often no more than salesspeak. Routing is routing, whether inter-VLAN or not. Routing is relaying based on layer 3 information. There are separate control planes (path determination) and forwarding planes (packet forwarding) in any router of reasonable performance. Layer 3 switches and routers are different names for a device that does the same thing. It might be argued that an inter-VLAN switch/router has to understand VLAN trunking protocols as well as layer 3 headers. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6125&t=6125 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: What do "interVLAN routing "and" Layer 3 switching " mean [7:6124]
I think that what you have described is "multi-layer" switching. As Howard has mentioned in past posts, L3S is simply a marketing term as is wire-speed switching. Layer 3 Switching is simply a line card, typically in a chassis-based system, that can make routing decisions (layer 3) using hardware-based technology (layer 2). By not relying on the fundamentally slow software decision making, this process greatly enhances the speed at which the decisions are made. There are other types of L3S devices, such as a 2948G-L3. This switch uses ASICs to make routing decisions within hardware. When you purchase one of these beasts, you basically have a 48-port gigabit router! Inter-VLAN routing is just routing. Basically, it can be performed with any routing-capable device so long as you have the appropriate interfaces. The difference between Inter-VLAn routing and legacy routing really has nothing to do with routing at all. The real difference is how the LANs have been broken out: either Layer 2 (VLANs) or Layer 3 (IP subnetting). If you know something about routing, then you know something about Inter-VLAN routing. Read up on VLANs (I suggest the Kenndy Clark CCIE switching book) and all will become clear. Rik -Original Message- From: Gareth Hinton [mailto:[EMAIL PROTECTED]] Sent: Monday, May 28, 2001 6:09 AM To: [EMAIL PROTECTED] Subject: Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6104] Hi Frank, I think the best description for Layer 3 Switching is "Route once - Switch many". The first time a packet in a particular "flow" passes through, a routing function will be used (on a different card, or even in a different device). But to speed up the processing of any further packets in that flow, a cache is created in the switch to remember this flow. The next time a packet comes through which matches this flow it will be switched without using the router functionality, therefore speeding things up. The definition of a flow can differ depending on configuration. For instance, normally a flow may be any packet to a particular destination, but if , for example, an extended access list is configured, the criteria for the flow may tighten up i.e. to be considered part of a flow, the source and destination are compared. Inter-VLAN routing means a packet gets routed every time. Regards, Gaz ""frank"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > What does the following mean ?it's cut from a description of WS-X4232-L3 on > cisco website. > > > The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN > routing for the Catalyst 4000 family switch and provides Layer 3 switching > between the Gigabit Ethernet interfaces. > > "John Hardman" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi > > > > OK I'll bite... > > > > Yes there is a difference. It gets a little convoluted, but there is a > > difference. > > > > L3 switching: Think of a L3 switch as a multi port router that operates at > > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet > > router. So L3 switching is routing traffic at wire speeds. You could use > one > > of these to route between VLANs, or route between networks. > > > > Inter-VLAN routing: This is a technique, technology that is only used to > > route traffic from one VLAN to other VLAN(s). It generally takes place at > > wire speeds inside a Cat switch with a L3 switch option, but is often see > > with routers that do not work at wire speeds. > > > > So the bottom line... think of a L3 switch as a device, and Inter-VLAN > > routing as a technology. > > > > HTH > > -- > > John Hardman CCNP MCSE > > > > > > ""frank"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Any difference? > > > > > > "frank" wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Thanks, > > > > > > > > > > > > Frank > > > > FAQ, list archives, and subscription info: > > > http://www.groupstudy.com/list/cisco.html > > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription inf
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6104]
Hi Frank, I think the best description for Layer 3 Switching is "Route once - Switch many". The first time a packet in a particular "flow" passes through, a routing function will be used (on a different card, or even in a different device). But to speed up the processing of any further packets in that flow, a cache is created in the switch to remember this flow. The next time a packet comes through which matches this flow it will be switched without using the router functionality, therefore speeding things up. The definition of a flow can differ depending on configuration. For instance, normally a flow may be any packet to a particular destination, but if , for example, an extended access list is configured, the criteria for the flow may tighten up i.e. to be considered part of a flow, the source and destination are compared. Inter-VLAN routing means a packet gets routed every time. Regards, Gaz ""frank"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > What does the following mean ?it's cut from a description of WS-X4232-L3 on > cisco website. > > > The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN > routing for the Catalyst 4000 family switch and provides Layer 3 switching > between the Gigabit Ethernet interfaces. > > "John Hardman" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hi > > > > OK I'll bite... > > > > Yes there is a difference. It gets a little convoluted, but there is a > > difference. > > > > L3 switching: Think of a L3 switch as a multi port router that operates at > > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet > > router. So L3 switching is routing traffic at wire speeds. You could use > one > > of these to route between VLANs, or route between networks. > > > > Inter-VLAN routing: This is a technique, technology that is only used to > > route traffic from one VLAN to other VLAN(s). It generally takes place at > > wire speeds inside a Cat switch with a L3 switch option, but is often see > > with routers that do not work at wire speeds. > > > > So the bottom line... think of a L3 switch as a device, and Inter-VLAN > > routing as a technology. > > > > HTH > > -- > > John Hardman CCNP MCSE > > > > > > ""frank"" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Any difference? > > > > > > "frank" wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Thanks, > > > > > > > > > > > > Frank > > > > FAQ, list archives, and subscription info: > > > http://www.groupstudy.com/list/cisco.html > > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6104&t=6104 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6094]
the following packet match the same rule will be directly switched by the L3-Swtich or MLS-enabled Switch. Inter-Vlan Routing: This is kind of routing. This first packet and the following packet will be routed by the router, not switch. So you will find the Inter-Vlan routing can not provide wire-speed forwarding. ** CCSI: 21130 XuJing ** ""frank"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Thanks, > > > Frank > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6094&t=6094 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6093]
the following packet match the same rule will be directly switched by the L3-Swtich or MLS-enabled Switch. Inter-Vlan Routing: This is kind of routing. This first packet and the following packet will be routed by the router, not switch. So you will find the Inter-Vlan routing can not provide wire-speed forwarding. ** CCSI: 21130 XuJing ** Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6093&t=6093 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6089]
What does the following mean ?it's cut from a description of WS-X4232-L3 on cisco website. The Catalyst 4003 and 4006 Layer 3 Services module provides interVLAN routing for the Catalyst 4000 family switch and provides Layer 3 switching between the Gigabit Ethernet interfaces. "John Hardman" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi > > OK I'll bite... > > Yes there is a difference. It gets a little convoluted, but there is a > difference. > > L3 switching: Think of a L3 switch as a multi port router that operates at > wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet > router. So L3 switching is routing traffic at wire speeds. You could use one > of these to route between VLANs, or route between networks. > > Inter-VLAN routing: This is a technique, technology that is only used to > route traffic from one VLAN to other VLAN(s). It generally takes place at > wire speeds inside a Cat switch with a L3 switch option, but is often see > with routers that do not work at wire speeds. > > So the bottom line... think of a L3 switch as a device, and Inter-VLAN > routing as a technology. > > HTH > -- > John Hardman CCNP MCSE > > > ""frank"" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Any difference? > > > > "frank" wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Thanks, > > > > > > > > > Frank > > > FAQ, list archives, and subscription info: > > http://www.groupstudy.com/list/cisco.html > > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6089&t=6089 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6084]
Hi OK I'll bite... Yes there is a difference. It gets a little convoluted, but there is a difference. L3 switching: Think of a L3 switch as a multi port router that operates at wire speed. The 2948G-L3 is an example. It is just a 50 port Ethernet router. So L3 switching is routing traffic at wire speeds. You could use one of these to route between VLANs, or route between networks. Inter-VLAN routing: This is a technique, technology that is only used to route traffic from one VLAN to other VLAN(s). It generally takes place at wire speeds inside a Cat switch with a L3 switch option, but is often see with routers that do not work at wire speeds. So the bottom line... think of a L3 switch as a device, and Inter-VLAN routing as a technology. HTH -- John Hardman CCNP MCSE ""frank"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Any difference? > > "frank" wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Thanks, > > > > > > Frank > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6084&t=6084 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
What do "interVLAN routing "and" Layer 3 switching " mean ?Any [7:6080]
Thanks, Frank Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6080&t=6080 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: What do "interVLAN routing "and" Layer 3 switching " mean [7:6082]
Any difference? "frank" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Thanks, > > > Frank > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=6082&t=6082 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Fw: Layer 3 Switching Flow Mask [7:3360]
- Original Message - From: Mr. Oletu Hosea Godswill, CCNA To: Ronny Jonathan Sent: Monday, May 07, 2001 6:18 PM Subject: Re: Layer 3 Switching Flow Mask [7:3360] > Me think since MLS has to do with layer 2 up to layer 4. We know that layer > 4 has ports numbers and all that. Ordinary if the ports numbers at layer 4 > at not made used of, MLS has not been accomplished. Access-list or something > have to be configured so that layer 4 element are used in the decision > making. Since this is the basic defination of MLS, it then means Flow mask > is an additional thing. > > I agree with what the cisco press book said, if you say > set mls flow destination > (only destination informations will be kept in the mls cache) > or if you say > set mls flow destination-source > (both source and destination ip-addresses will be kept in the mls cache) > better stil > set mls flow full > (All informations including port numbers will be documented in the cache) > > Good luck, > (Also preparing for BCMSN) > > my 2 cents. > Oletu > > > > - Original Message - > From: Ronny Jonathan > To: > Sent: Sunday, May 06, 2001 12:10 PM > Subject: Layer 3 Switching Flow Mask [7:3360] > > > > Hi All, > > > > In BCMSN course book (Cisco Press) p233, it is stated that: > > "Most Cisco documentation explains flow masks as a way to determine how > > packets are compared to entries in the MLS cache. This is inaccurate. Flow > > masks are actually used to determine how much information about the packet > is > > placed in the MLS cache. The flow mask is not used to compare packets to > > existing entries in the MLS cache" > > > > But from another source (Boson & Cisco Doc): > > "you are introducing policy based routing and want to route differently > based > > on source, destination, and port number. What command would you use on a > > multi-level switch to make it consider port numbers when layer 3 > forwarding ? > > the correct syntax is: set mls flow [destination|destination-source|full]. > > > http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/m > l > > s.htm#xtocidll0l940" > > > > So the command "set mls flow ...", is it only to determine what > information > > to > > be kept in the mls entry or is it meant to enforce so that all packets > going > > through the L3 switch will be compared to the mls entry according to the > flow > > mask that has been set up by the "set mls flow" command ? > > > > Thanks in advance for the answer, I need it for BCMSN exam on Wednesday. > > > > Regards, > > Ronny > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > _ > Do You Yahoo!? > Get your free @yahoo.com address at http://mail.yahoo.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=3439&t=3360 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 Switching Flow Mask [7:3360]
First, thanks for your answer Drew ... but I'm still confused ... > It determines what information > is stored in the mls entry and enforces all packets > coming through the mls > switch to be compared with the entry according to > the flow mask specified > with set mls flow. How about the note in the BCMSN course book. My interpretation for the note is: The "set mls flow" is to determine what information to be stored in the mls entry (for statistic and data collection purpose), but NOT to enforce packets that go through the mls switch to be compared with the mls entry according to the flow mask specified by the command. > By the way, there is a difference between an L3 > switch and an mls-capable > switch. Make sure you don't get those confused. What is the different ? Are you referring to the RSM/RSFC/MSM/MSFC (MLS-RP) for the layer 3 switch and Cat 5000/6000(MLS-SE) for the mls-capable switch ? Regards, Ronny __ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/ Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=3378&t=3360 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Layer 3 Switching Flow Mask [7:3360]
Hi All, In BCMSN course book (Cisco Press) p233, it is stated that: "Most Cisco documentation explains flow masks as a way to determine how packets are compared to entries in the MLS cache. This is inaccurate. Flow masks are actually used to determine how much information about the packet is placed in the MLS cache. The flow mask is not used to compare packets to existing entries in the MLS cache" But from another source (Boson & Cisco Doc): "you are introducing policy based routing and want to route differently based on source, destination, and port number. What command would you use on a multi-level switch to make it consider port numbers when layer 3 forwarding ? the correct syntax is: set mls flow [destination|destination-source|full]. http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/ml s.htm#xtocidll0l940" So the command "set mls flow ...", is it only to determine what information to be kept in the mls entry or is it meant to enforce so that all packets going through the L3 switch will be compared to the mls entry according to the flow mask that has been set up by the "set mls flow" command ? Thanks in advance for the answer, I need it for BCMSN exam on Wednesday. Regards, Ronny Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=3360&t=3360 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Layer 3 Switching [7:1222]
I am trying to find out about switching on the CCIE lab exam, is there a particular focus on layer 2 using the set commands, or is it a mix of both? I am just trying to get an overview of what I need to pass the test, should I buy the RSM for the Catalyst 500, or should I save my money. Any help would be appreciated. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=1222&t=1222 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Confuse about Fast Switching and Layer 3 switching
>Stuart, > >I do not think any packets could be switched without CPU. Fast switching >needs CPU, it just does not need the CPU to call the ip input process. If >the router needs to search the routing table, it will need ip input process, >other than that, the CPU can use cache during one interrupt. As you >mentioned there are different cache, it all depends on how the router creats >them. >Just my 2 cents. > >Thanks >Jack Distributed CEF, distributed NetFlow, silicon, autonomous, and arguably optimum switching get at least some of the forwarding out of the main processor. Typically, the first packet to a destination goes through the main processor, and creates a cache entry that will be used for subsequent packets. dCEF is a little different, in that it creates FIBs that mirror the RIB, so, once routing protocols or other mechanisms put a destination into the RIB, the FIBs change in response. There is no need to wait for a first packet. > > >""Stuart Potts"" <[EMAIL PROTECTED]> wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... >> Hi, >> >> Brief: >> >> Fast switching is as follows, 1st packet is processed switched, 2 packet >to > > destination is fast switched. i.e. it never goes through the cpu. The fast switched packets do go through the CPU, but their destination is looked up in a cache that is faster for lookup than the main routing table. Fast switching, for other reasons, do reduce the CPU load. > > >> L3 switching , MLS, Multi layer switching, This is based on traffic flows, >> ie we could swich on a certain tcp flow, or certain source/detination and >> destination port. as defined by access lists. >> >> The three flow masks are as follows: >> >> destination-ipóThe least-specific flow mask. The MLS-SE maintains one MLS >> entry for each destination IP address. All flows to a given destination IP >> address use this MLS entry. This mode is used if there are no access lists >> configured on any of the MLS-RP interfaces. >> >> source-destination-ipóThe MLS-SE maintains one MLS entry for each source >and >> destination IP address pair. All flows between a given source and >> destination use this MLS entry regardless of the IP protocol ports. This >> mode is used if there is a standard access list on any of the MLS-RP >> interfaces. >> >> ip-flowóThe most-specific flow mask. The MLS-SE creates and maintains a >> separate MLS cache entry for every IP flow. An ip-flow entry includes the >> source IP address, destination IP address, protocol, and protocol ports. >> This mode is used if there is an extended access list on any of the MLS-RP >> interfaces. >> >> >> >> >http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/m >> ls.htm#xtocid171391 >> >> http://www.cisco.com/warp/customer/473/55.html >> > > /Stuart. >> > > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Confuse about Fast Switching and Layer 3 switching
Stuart, I do not think any packets could be switched without CPU. Fast switching needs CPU, it just does not need the CPU to call the ip input process. If the router needs to search the routing table, it will need ip input process, other than that, the CPU can use cache during one interrupt. As you mentioned there are different cache, it all depends on how the router creats them. Just my 2 cents. Thanks Jack ""Stuart Potts"" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hi, > > Brief: > > Fast switching is as follows, 1st packet is processed switched, 2 packet to > destination is fast switched. i.e. it never goes through the cpu. > > L3 switching , MLS, Multi layer switching, This is based on traffic flows, > ie we could swich on a certain tcp flow, or certain source/detination and > destination port. as defined by access lists. > > The three flow masks are as follows: > > destination-ipThe least-specific flow mask. The MLS-SE maintains one MLS > entry for each destination IP address. All flows to a given destination IP > address use this MLS entry. This mode is used if there are no access lists > configured on any of the MLS-RP interfaces. > > source-destination-ipThe MLS-SE maintains one MLS entry for each source and > destination IP address pair. All flows between a given source and > destination use this MLS entry regardless of the IP protocol ports. This > mode is used if there is a standard access list on any of the MLS-RP > interfaces. > > ip-flowThe most-specific flow mask. The MLS-SE creates and maintains a > separate MLS cache entry for every IP flow. An ip-flow entry includes the > source IP address, destination IP address, protocol, and protocol ports. > This mode is used if there is an extended access list on any of the MLS-RP > interfaces. > > > > http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/m > ls.htm#xtocid171391 > > http://www.cisco.com/warp/customer/473/55.html > > /Stuart. > > > - > > | | Stuart Potts > ||| ||| Customer Support Engineer > .|. .|. >.:|:.:|:. > c i s c o S y s t e m s Email: [EMAIL PROTECTED] > > "Empowering the Internet Generation" > - > > > > > > > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > Dove > Sent: Wednesday, March 07, 2001 7:02 AM > To: [EMAIL PROTECTED] > Subject: Confuse about Fast Switching and Layer 3 switching > > > Hi, > > I have some confuse about the "Fast Switching" and "Layer 3 switching". Both > of them are mentioned that route first packet and switch others. Could > anyone please help me? > > Regards. > dovelet > > > _ > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Confuse about Fast Switching and Layer 3 switching
Hi, Brief: Fast switching is as follows, 1st packet is processed switched, 2 packet to destination is fast switched. i.e. it never goes through the cpu. L3 switching , MLS, Multi layer switching, This is based on traffic flows, ie we could swich on a certain tcp flow, or certain source/detination and destination port. as defined by access lists. The three flow masks are as follows: destination-ipThe least-specific flow mask. The MLS-SE maintains one MLS entry for each destination IP address. All flows to a given destination IP address use this MLS entry. This mode is used if there are no access lists configured on any of the MLS-RP interfaces. source-destination-ipThe MLS-SE maintains one MLS entry for each source and destination IP address pair. All flows between a given source and destination use this MLS entry regardless of the IP protocol ports. This mode is used if there is a standard access list on any of the MLS-RP interfaces. ip-flowThe most-specific flow mask. The MLS-SE creates and maintains a separate MLS cache entry for every IP flow. An ip-flow entry includes the source IP address, destination IP address, protocol, and protocol ports. This mode is used if there is an extended access list on any of the MLS-RP interfaces. http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/layer3/m ls.htm#xtocid171391 http://www.cisco.com/warp/customer/473/55.html /Stuart. - | | Stuart Potts ||| ||| Customer Support Engineer .|. .|. .:|:.:|:. c i s c o S y s t e m s Email: [EMAIL PROTECTED] "Empowering the Internet Generation" - -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Dove Sent: Wednesday, March 07, 2001 7:02 AM To: [EMAIL PROTECTED] Subject: Confuse about Fast Switching and Layer 3 switching Hi, I have some confuse about the "Fast Switching" and "Layer 3 switching". Both of them are mentioned that route first packet and switch others. Could anyone please help me? Regards. dovelet _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Confuse about Fast Switching and Layer 3 switching
Hi, I have some confuse about the "Fast Switching" and "Layer 3 switching". Both of them are mentioned that route first packet and switch others. Could anyone please help me? Regards. dovelet _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Layer 3 switching
Muhammad Asif Rashid wrote: > > Any 6500 series switch can be a layer 3 switch as well as the 3500 > series and 2900 series, I believe. With many limitations. Check the documentation. It depends on the environment you want to put the switch into. Same for 2948G-L3 and other "layer 3" devices from Cisco (and other vendors for that matter). You gain lots of speed but lose a lot of traditionl IOS router functionality. Jeff Kell <[EMAIL PROTECTED]> _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching
Any 6500 series switch can be a layer 3 switch as well as the 3500 series and 2900 series, I believe. Thanks, -- ** Q. Wade Billings Product Operations Manager Excite@Home - The Leader in Broadband _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: LAYER 3 SWITCHING
FRS, Layer 3 Switching, is not a situation when the CPU isn't involvedThat is Fast Switching, This is actually when routing information is stored in CACHE memory and it is processed without running as many interrupts to the CPU. And YES L3 switching does have everything to do with L2 frames.If it didn't then switches wouldn't be involved[ Layer 3 Switching ] consists of the MLSP Protocol < Muli-Layer Switching Protocol >...What happens is when you have a < Switch(s) / Router > where the Switches have redundant connections to one another and you are running Vlans between the Switches, what do they have to do to get to the other Vlan; they have to go to the router for the packe to be routed since our Vlans are on different subnets.Well what happens is that your switches build a CACHE entry in their MLS Cache and from the information that's in the packet that's stripped they see what port that it was sent out, and they also have the MAC Addresses of the Destination / Source / Port #; just depending on if your running Dst / Src / Port Layer Switching. They then add this to their CACHE entry database and they then switch the packets from there on.Also there is a limited time that this information will stay in the L3 Cache Database ( 256 seconds ) if I remember correctly. Your able to base the switching on Destination / Destination-Source / Destination-Source-Port so then you would actually be doing L4 Switching. HTH. JEK "FRS" <[EMAIL PROTECTED]> wrote in message 8qu1br$9th$[EMAIL PROTECTED]">news:8qu1br$9th$[EMAIL PROTECTED]... > I need some help in understanding Layer 3 Switching. > > 1. What does the process Layer 3 switching refer to? > > 2. Is it packets or frames being switched out of interfaces or ports? > > 3. Using the 2948G-L3 as an example, how is the switching determined - by > Routing table or CAM table? > > All help is appreciated. > > > **NOTE: New CCNA/CCDA List has been formed. For more information go to > http://www.groupstudy.com/list/Associates.html > _ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
overview of Layer 3 switching & routing
Found this interesting link. It wanders a little from the "Layer-3 Switching" subject, but as newbie I found it interesting. http://www.cisco.com/warp/public/cc/so/neso/lnso/cpso/l3c85_wp.htm Dave **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Layer 3 switching
> Any 6500 series switch can be a layer 3 switch as well as the 3500 > series and 2900 series, I believe. No. 2900XL and 3500XL run IOS, but canoot perform any routing services. To clarify on your other statement, ANY model in the 6000 series will perform "Layer 3 switching" as long as you have a Supervisor with an MSFC. A 6500 chassis is not specifically required. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: LAYER 3 SWITCHING
Cisco's "layer 3 switching", simply put, refers to all routing processes except process switching (conventional routing with CPU). Namely, any routing process without CPU's intervention is considered "layer 3 switching". This has nothing to do with frames (layer 2) obviously. HTH, Rog > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > FRS > Sent: Wednesday, September 27, 2000 7:55 PM > To: [EMAIL PROTECTED] > Subject: LAYER 3 SWITCHING > > > I need some help in understanding Layer 3 Switching. > > 1. What does the process Layer 3 switching refer to? > > 2. Is it packets or frames being switched out of interfaces or ports? > > 3. Using the 2948G-L3 as an example, how is the switching determined - by > Routing table or CAM table? > > All help is appreciated. > > > **NOTE: New CCNA/CCDA List has been formed. For more information go to > http://www.groupstudy.com/list/Associates.html > _ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: LAYER 3 SWITCHING
> 1. What does the process Layer 3 switching refer to? "switching" has become a convuluted term. "switching", in marketing-speak, means "fast" for all intents and purposes. Thus, "L3 switching" is "fast routing". Have fun. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: LAYER 3 SWITCHING
Title: RE: LAYER 3 SWITCHING Well here are my answers, I wager $700.00 of Jeopardy money. 1. Layer 3 switching is actually routing. It is designed for high speed routing however. 2. For the answer to this question remember your encapsulation from CCNA - Data->segments->packets->frames->bits and back the other way for receiving. So switch would use frames, whereas a layer 3 switch which is really a router, would switch packets. If this is incorrect feel free to let me know. 3. And I just plain don't know without looking anything up on this on. Joey -Original Message- From: FRS [mailto:[EMAIL PROTECTED]] Sent: Wednesday, September 27, 2000 7:55 PM To: [EMAIL PROTECTED] Subject: LAYER 3 SWITCHING I need some help in understanding Layer 3 Switching. 1. What does the process Layer 3 switching refer to? 2. Is it packets or frames being switched out of interfaces or ports? 3. Using the 2948G-L3 as an example, how is the switching determined - by Routing table or CAM table? All help is appreciated. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: LAYER 3 SWITCHING
The answer is, every Cisco switch implements it differently. Try this link, it gives a basic explanation of each switch's method. http://www.cisco.com/warp/public/784/packet/july98/12.html Steve -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of FRS Sent: Wednesday, September 27, 2000 6:55 PM To: [EMAIL PROTECTED] Subject: LAYER 3 SWITCHING I need some help in understanding Layer 3 Switching. 1. What does the process Layer 3 switching refer to? 2. Is it packets or frames being switched out of interfaces or ports? 3. Using the 2948G-L3 as an example, how is the switching determined - by Routing table or CAM table? All help is appreciated. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
LAYER 3 SWITCHING
I need some help in understanding Layer 3 Switching. 1. What does the process Layer 3 switching refer to? 2. Is it packets or frames being switched out of interfaces or ports? 3. Using the 2948G-L3 as an example, how is the switching determined - by Routing table or CAM table? All help is appreciated. **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching
Quoth someone below:"2948G-L3 -- Basically a 48-port router!" Yes, as aforementioned, the 2948G-L3 *can* reside quite readily in Layer 3 land, and configured that way, per port. But, L3 land isn't really switch land, and to just view the G-L3 as a 48 port high-speed router is not getting your Cisco 'bang-for-the-buck". Don't forget ISL/802.1q, VLAN fun, I)ntegrated R)outing and B)ridging and B)ridge V)irtual I)nterfaces. Those nifty, but, for me at least, complex integrations, are a real instructive challenge to your BCSN tasks. The 2948G-L3 is a fairly new addition to the fleet. To that end, there are a couple of URLs providing *some* guidance for setup. Be warned, however, that a good grasp of Cisco LAN Switching should be a prerequisite. Oddly enough, Cisco Press has a book of that title. It's a worthy read. http://www.cisco.com/warp/public/473/25.html http://www.cisco.com/warp/public/473/29.html <http://www.cisco.com/warp/public/473/29.html> http://www.cisco.com/univercd/cc/td/doc/product/l3sw/2948g-l3/rel_12_0/7wx51 5a/config_g/bridging.htm#23388 <http://www.cisco.com/univercd/cc/td/doc/product/l3sw/2948g-l3/rel_12_0/7wx5 15a/config_g/bridging.htm#23388> There is one other link at the Cisco site concerning ISL links to a 2924XL. Don't have that one handy. If any of you gentle readers have some more sample configs, please don't hesitate to contact me, as I'm still fighting the battle. Best, G. "Be strict in what you send, and forgiving in what you receive." -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- George Hartnell, Network Supervisor Bellingham School District, 1306 DuPont St. Bellingham, Wa. 98225-3198 (360)647-6860 [EMAIL PROTECTED] Internet Mail -Original Message- From: Guyler, Rik [EESUS] [mailto:[EMAIL PROTECTED]] Sent: Wednesday, September 27, 2000 9:00 AM To: Cisco Groupstudy (E-mail) Subject: RE: Layer 3 switching 2948G-L3 -- Basically a 48-port router! -Original Message- From: Fowler, Joey [mailto:[EMAIL PROTECTED]] Sent: Wednesday, September 27, 2000 11:19 AM To: [EMAIL PROTECTED] Subject: Layer 3 switching I know there has been much discussion on this in the past, but I want to make sure that I understand it. Layer 3 switching is the equivalent of routing, but is usually referred to as Layer 3 switching because it's designed for high speed LAN traffic. Assuming the above is correct what are some examples of a regular routers vs. layer 3 switch? I'm guessing the 2500 series routers would be regular but what would be a good example of a layer 3 switch? Thanks, Joey Fowler Senior Network Engineer Foodtrader.com **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching
Title: Layer 3 switching
OK, no
argument from me. It's still Multi-layer switching, not layer 3
switching.
Steve
-Original Message-From: Abruzzese, John
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27,
2000 1:56 PMTo: Steve and Monica BrokawCc: Cisco Group
Study (E-mail)Subject: RE: Layer 3 switching
In
the 6000 family the MSFC acts as the MLS-RP, the equivalent of an RSM or Layer
3 router, and the Policy Feature Card(PFC) acts as the MLS-SE, which basically
is the equivalent of the Net Flow Feature Card(NFFC) in the Cat 5000
family.
-Original Message-From: Steve and Monica Brokaw
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27,
2000 2:48 PMTo: Abruzzese, John;
[EMAIL PROTECTED]Subject: RE: Layer 3
switching
OK, maybe this is a question of semantics, maybe I'll get flamed, but
here goes anyway. The 6000 series does Multilayer switching, which is
quite different in its functionality than layer 3 switching.
Multilayer switching must still have a layer 3 router available to making
the initial routing decision for a flow. True layer 3 switching uses
ASICS to perform the routing functionality.
Steve Brokaw, MCSE CCNA CCNP
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Abruzzese,
JohnSent: Wednesday, September 27, 2000 12:37 PMTo:
Cisco Group Study (E-mail)Subject: FW: Layer 3
switching
-Original Message-From: Abruzzese, John
Sent: Wednesday, September 27, 2000 1:36 PMTo: Iohan
ReyesSubject: RE: Layer 3 switching
The Catalyst 6000 switch family will do layer 3
switching with the Multi-Layer Switching Card(MSFC) and the Policy Feature
Card(PFC). You can do both Layer 2 & 3 switching in addition to access
lists.
-Original Message-From: Iohan Reyes
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000
12:45 PMTo: Fowler, Joey;
[EMAIL PROTECTED]Subject: RE: Layer 3
switching
I believe the 6000 series can be outfitted with a module to make
it a layer-3 switch...
-Original Message-From:
[EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
Fowler, JoeySent: Wednesday, September 27, 2000 11:19
AMTo: [EMAIL PROTECTED]Subject: Layer 3
switching
I know there has been much discussion on
this in the past, but I want to make sure that I understand it.
Layer 3 switching is the equivalent of routing, but is usually
referred to as Layer 3 switching because it's designed for high speed
LAN traffic.
Assuming the above is correct what are some
examples of a regular routers vs. layer 3 switch? I'm guessing the
2500 series routers would be regular but what would be a good example
of a layer 3 switch?
Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
RE: Layer 3 switching
Title: Layer 3 switching
In the
6000 family the MSFC acts as the MLS-RP, the equivalent of an RSM or Layer 3
router, and the Policy Feature Card(PFC) acts as the MLS-SE, which basically is
the equivalent of the Net Flow Feature Card(NFFC) in the Cat 5000
family.
-Original Message-From: Steve and Monica Brokaw
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000
2:48 PMTo: Abruzzese, John; [EMAIL PROTECTED]Subject:
RE: Layer 3 switching
OK,
maybe this is a question of semantics, maybe I'll get flamed, but here goes
anyway. The 6000 series does Multilayer switching, which is quite
different in its functionality than layer 3 switching. Multilayer
switching must still have a layer 3 router available to making the initial
routing decision for a flow. True layer 3 switching uses ASICS to
perform the routing functionality.
Steve Brokaw, MCSE CCNA CCNP
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Abruzzese,
JohnSent: Wednesday, September 27, 2000 12:37 PMTo:
Cisco Group Study (E-mail)Subject: FW: Layer 3
switching
-Original Message-From: Abruzzese, John
Sent: Wednesday, September 27, 2000 1:36 PMTo: Iohan
ReyesSubject: RE: Layer 3 switching
The Catalyst 6000 switch family will do layer 3
switching with the Multi-Layer Switching Card(MSFC) and the Policy Feature
Card(PFC). You can do both Layer 2 & 3 switching in addition to access
lists.
-Original Message-From: Iohan Reyes
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000
12:45 PMTo: Fowler, Joey;
[EMAIL PROTECTED]Subject: RE: Layer 3
switching
I believe the 6000 series can be outfitted with a module to make it
a layer-3 switch...
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Fowler,
JoeySent: Wednesday, September 27, 2000 11:19
AMTo: [EMAIL PROTECTED]Subject: Layer 3
switching
I know there has been much discussion on this
in the past, but I want to make sure that I understand it. Layer 3
switching is the equivalent of routing, but is usually referred to as
Layer 3 switching because it's designed for high speed LAN
traffic.
Assuming the above is correct what are some
examples of a regular routers vs. layer 3 switch? I'm guessing the 2500
series routers would be regular but what would be a good example of a
layer 3 switch?
Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
RE: Layer 3 switching
Title: Layer 3 switching
OK,
maybe this is a question of semantics, maybe I'll get flamed, but here goes
anyway. The 6000 series does Multilayer switching, which is quite
different in its functionality than layer 3 switching. Multilayer
switching must still have a layer 3 router available to making the initial
routing decision for a flow. True layer 3 switching uses ASICS to perform
the routing functionality.
Steve
Brokaw, MCSE CCNA CCNP
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Abruzzese,
JohnSent: Wednesday, September 27, 2000 12:37 PMTo:
Cisco Group Study (E-mail)Subject: FW: Layer 3
switching
-Original Message-From: Abruzzese, John
Sent: Wednesday, September 27, 2000 1:36 PMTo: Iohan
ReyesSubject: RE: Layer 3 switching
The
Catalyst 6000 switch family will do layer 3 switching with the Multi-Layer
Switching Card(MSFC) and the Policy Feature Card(PFC). You can do both Layer 2
& 3 switching in addition to access lists.
-Original Message-From: Iohan Reyes
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000 12:45
PMTo: Fowler, Joey; [EMAIL PROTECTED]Subject: RE:
Layer 3 switching
I
believe the 6000 series can be outfitted with a module to make it a layer-3
switch...
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Fowler,
JoeySent: Wednesday, September 27, 2000 11:19 AMTo:
[EMAIL PROTECTED]Subject: Layer 3
switching
I know there has been much discussion on this
in the past, but I want to make sure that I understand it. Layer 3
switching is the equivalent of routing, but is usually referred to as
Layer 3 switching because it's designed for high speed LAN
traffic.
Assuming the above is correct what are some
examples of a regular routers vs. layer 3 switch? I'm guessing the 2500
series routers would be regular but what would be a good example of a
layer 3 switch?
Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
RE: Layer 3 switching
Please correct me if I am wrong, but aren't the 2900 and 3500 layer 2 only? -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Q Wade Billings Sent: Wednesday, September 27, 2000 1:40 PM To: [EMAIL PROTECTED] Subject: RE: Layer 3 switching Any 6500 series switch can be a layer 3 switch as well as the 3500 series and 2900 series, I believe. Thanks, -- ** Q. Wade Billings Product Operations Manager Excite@Home - The Leader in Broadband **NOTE: New CCNA/CCDA List has been formed. For more information go to http://www.groupstudy.com/list/Associates.html _ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching
Title: Layer 3 switching 6000 series switch, 5500, 4006 have a router module to put in it. -Original Message-From: Iohan Reyes [mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000 12:45 PMTo: Fowler, Joey; [EMAIL PROTECTED]Subject: RE: Layer 3 switching I believe the 6000 series can be outfitted with a module to make it a layer-3 switch... -Original Message-From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Fowler, JoeySent: Wednesday, September 27, 2000 11:19 AMTo: [EMAIL PROTECTED]Subject: Layer 3 switching I know there has been much discussion on this in the past, but I want to make sure that I understand it. Layer 3 switching is the equivalent of routing, but is usually referred to as Layer 3 switching because it's designed for high speed LAN traffic. Assuming the above is correct what are some examples of a regular routers vs. layer 3 switch? I'm guessing the 2500 series routers would be regular but what would be a good example of a layer 3 switch? Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
FW: Layer 3 switching
Title: Layer 3 switching
-Original Message-From: Abruzzese, John
Sent: Wednesday, September 27, 2000 1:36 PMTo: Iohan
ReyesSubject: RE: Layer 3 switching
The
Catalyst 6000 switch family will do layer 3 switching with the Multi-Layer
Switching Card(MSFC) and the Policy Feature Card(PFC). You can do both Layer 2
& 3 switching in addition to access lists.
-Original Message-From: Iohan Reyes
[mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000 12:45
PMTo: Fowler, Joey; [EMAIL PROTECTED]Subject: RE:
Layer 3 switching
I
believe the 6000 series can be outfitted with a module to make it a layer-3
switch...
-Original Message-From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Fowler,
JoeySent: Wednesday, September 27, 2000 11:19 AMTo:
[EMAIL PROTECTED]Subject: Layer 3
switching
I know there has been much discussion on this in
the past, but I want to make sure that I understand it. Layer 3
switching is the equivalent of routing, but is usually referred to as Layer
3 switching because it's designed for high speed LAN traffic.
Assuming the above is correct what are some
examples of a regular routers vs. layer 3 switch? I'm guessing the 2500
series routers would be regular but what would be a good example of a layer
3 switch?
Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
RE: Layer 3 switching
Any 6500 series switch can be a layer 3 switch as well as the 3500 series and 2900 series, I believe. Thanks, -- ** Q. Wade Billings Product Operations Manager Excite@Home - The Leader in Broadband begin:vcard n:Billings;Q. Wade tel;fax:801 234-8350 tel;work:801 234-8316 x-mozilla-html:FALSE org:Excite Business Applications;Product Operations adr:;;700 East Technology Ave;Orem;Utah;84097;USA version:2.1 email;internet:[EMAIL PROTECTED] title:Product Operations Manager fn:Q. Wade Billings end:vcard
RE: Layer 3 switching
Title: Layer 3 switching I believe the 6000 series can be outfitted with a module to make it a layer-3 switch... -Original Message-From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Fowler, JoeySent: Wednesday, September 27, 2000 11:19 AMTo: [EMAIL PROTECTED]Subject: Layer 3 switching I know there has been much discussion on this in the past, but I want to make sure that I understand it. Layer 3 switching is the equivalent of routing, but is usually referred to as Layer 3 switching because it's designed for high speed LAN traffic. Assuming the above is correct what are some examples of a regular routers vs. layer 3 switch? I'm guessing the 2500 series routers would be regular but what would be a good example of a layer 3 switch? Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
RE: Layer 3 switching
Title: Layer 3 switching 2948G-L3 -- Basically a 48-port router! -Original Message-From: Fowler, Joey [mailto:[EMAIL PROTECTED]]Sent: Wednesday, September 27, 2000 11:19 AMTo: [EMAIL PROTECTED]Subject: Layer 3 switching I know there has been much discussion on this in the past, but I want to make sure that I understand it. Layer 3 switching is the equivalent of routing, but is usually referred to as Layer 3 switching because it's designed for high speed LAN traffic. Assuming the above is correct what are some examples of a regular routers vs. layer 3 switch? I'm guessing the 2500 series routers would be regular but what would be a good example of a layer 3 switch? Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
Layer 3 switching
Title: Layer 3 switching I know there has been much discussion on this in the past, but I want to make sure that I understand it. Layer 3 switching is the equivalent of routing, but is usually referred to as Layer 3 switching because it's designed for high speed LAN traffic. Assuming the above is correct what are some examples of a regular routers vs. layer 3 switch? I'm guessing the 2500 series routers would be regular but what would be a good example of a layer 3 switch? Thanks, Joey Fowler Senior Network Engineer Foodtrader.com
Re: Layer 3 switching vs. Layer 4 switching?
Francis, The process you have described looks more like "load-balancing"/"load-sharing" - Cisco LocalDirector supports that kind of traffic management. It seems that Layer4 switches do a bit difeerent thing (though mosty of them do load-balancing). We use FoundryNetworks Layer 4 switches in some of our implementatios for redirecting traffic to the WebFilter/cach engine. The switch is able to redirect packets on per-tcp-port basis. For example we have configured ours to redirect all http requests to the WebCache engines and let everything else through RGRDS, Evgeny ""Arigo, Francis"" <[EMAIL PROTECTED]> wrote in message 304545310AD0D3118F9900600897AD9A07743B@GALILEO">news:304545310AD0D3118F9900600897AD9A07743B@GALILEO... > We use an Alteon Web Switch that uses "layer 4 switching". I don't know if > the concept is the same for cisco switches, but this is how it works on the > Alteon: > > Each web site is assigned a "virtual IP" that is not assigned to any host; > it is defined in the switch config. Then we have the web servers that have > different real IP addresses. When someone requests a web page, it resolves > to the "virtual IP" address. Then the Alteon does some processes in Layer 4 > to determine which web server has the least load, then routes the request to > that server. > > I'm sure that Layer 4 switching is not limited to just web switching, but I > haven't seen it used for anything else. Does anyone else have any experience > with it? > > Hope that helps with the concept, > Francis Arigo, MCSE, CCNA > System Administrator > Classroom Connect > > -----Original Message- > From: Ms. Maria [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, June 14, 2000 7:58 PM > To: [EMAIL PROTECTED] > Subject: Layer 3 switching vs. Layer 4 switching? > > > Hi, > > I was reading Karen Webb book on Building Cisco Multilayer Switched Networks > > (BCMSN). I came across some information on Layer 4 switching that somehow I > didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware > based routing that consider the applications. " > I understand the Layer 3 switching that is not logical and etc. But what > about Layer 4 switching??? What new Switches and Routers are supporting > Layer 4 (Transport Layer) switching? > If Layer 3 and Layer 4 switching is same than is there any difference? > Any responses are welcome on this topic. > > Thanks for your time! > > Maria > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching vs. Layer 4 switching?
I would think the process of directing to the lest loaded server would be higher in the stack than level 4. Except that the Alteon uses some statefull firewall like table where it remembers the sessions going in to each server, it would probably work best if all the servers are of alike power, wouldn't it? Also, most applications that need a certain QoS would need higher layer switching, as L3 alone won't cut it. Francisco Muniz "Arigo, Francis" <[EMAIL PROTECTED]> escribió en el mensaje de noticias [EMAIL PROTECTED] > We use an Alteon Web Switch that uses "layer 4 switching". I don't know if > the concept is the same for cisco switches, but this is how it works on the > Alteon: > > Each web site is assigned a "virtual IP" that is not assigned to any host; > it is defined in the switch config. Then we have the web servers that have > different real IP addresses. When someone requests a web page, it resolves > to the "virtual IP" address. Then the Alteon does some processes in Layer 4 > to determine which web server has the least load, then routes the request to > that server. > > I'm sure that Layer 4 switching is not limited to just web switching, but I > haven't seen it used for anything else. Does anyone else have any experience > with it? > > Hope that helps with the concept, > Francis Arigo, MCSE, CCNA > System Administrator > Classroom Connect > > -Original Message- > From: Ms. Maria [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, June 14, 2000 7:58 PM > To: [EMAIL PROTECTED] > Subject: Layer 3 switching vs. Layer 4 switching? > > > Hi, > > I was reading Karen Webb book on Building Cisco Multilayer Switched Networks > > (BCMSN). I came across some information on Layer 4 switching that somehow I > didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware > based routing that consider the applications. " > I understand the Layer 3 switching that is not logical and etc. But what > about Layer 4 switching??? What new Switches and Routers are supporting > Layer 4 (Transport Layer) switching? > If Layer 3 and Layer 4 switching is same than is there any difference? > Any responses are welcome on this topic. > > Thanks for your time! > > Maria > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching vs. Layer 4 switching?
We use an Alteon Web Switch that uses "layer 4 switching". I don't know if the concept is the same for cisco switches, but this is how it works on the Alteon: Each web site is assigned a "virtual IP" that is not assigned to any host; it is defined in the switch config. Then we have the web servers that have different real IP addresses. When someone requests a web page, it resolves to the "virtual IP" address. Then the Alteon does some processes in Layer 4 to determine which web server has the least load, then routes the request to that server. I'm sure that Layer 4 switching is not limited to just web switching, but I haven't seen it used for anything else. Does anyone else have any experience with it? Hope that helps with the concept, Francis Arigo, MCSE, CCNA System Administrator Classroom Connect -Original Message- From: Ms. Maria [mailto:[EMAIL PROTECTED]] Sent: Wednesday, June 14, 2000 7:58 PM To: [EMAIL PROTECTED] Subject: Layer 3 switching vs. Layer 4 switching? Hi, I was reading Karen Webb book on Building Cisco Multilayer Switched Networks (BCMSN). I came across some information on Layer 4 switching that somehow I didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware based routing that consider the applications. " I understand the Layer 3 switching that is not logical and etc. But what about Layer 4 switching??? What new Switches and Routers are supporting Layer 4 (Transport Layer) switching? If Layer 3 and Layer 4 switching is same than is there any difference? Any responses are welcome on this topic. Thanks for your time! Maria Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: good books on Layer 3 switching
That is a common Extreme sales pitch. If most/all of the traffic in the closet is going to the core, then why do you need layer 3 in the closet? Are you going to put every desktop on it's own subnet? :) Layer 3 in the closet really doesn't make sense in most installations. Cisco just released the 2948G-L3 but I still wouldn't put layer 3 in a closet unless there was a real need for it. <http://www.cisco.com/univercd/cc/td/doc/product/l3sw/2948g-l3/index.htm> <http://www.cisco.com/univercd/cc/td/doc/pcat/ca2948g.htm> For a good reference on Layer 3 switching, check out this link on Cisco's website. <http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_5_4/msfc/index.htm> Kevin At 07:37 AM 6/12/00 -0400, Brian Hartsfield wrote: >I'm wondering if anybody can point me to some good books on layer 3 >switching that gets into technical details on QoS, design, that type of >stuff. We are looking at replacing some of our shared 10 Meg equipment >with 10/100 switches and we are looking at some layer 3 equipment. I am >familiar with routing in routers, but the layer 3 switching stuff is a >little different as far as how you design things and so forth. Things are >complicated by the fact that we had an Extreme Networks rep come in and >convince everybody that you have to have layer 3 switches all the way to >the wiring closet, but I don't know enough about layer 3 right now to know >if that is true or not so I need to get up to speed on the details of >layer 3 and how to best design a layer 3 type network (ex. layer 3 in the >core only or all the way out to the wiring closet) so if anybody has any >good books on the topic they could point me to I would greatly appreciate >it. Thanks. > >Brian > >___ >UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html >FAQ, list archives, and subscription info: http://www.groupstudy.com >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] - Kevin S. Mahler, CCNP, CCDA, CCSE Systems Engineer, Cisco Systems Atlanta, GA See my homepage at <http://www.kmahler.com> What does not destroy me, makes me stronger. -- Friedrich Nietzsche ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
good books on Layer 3 switching
I'm wondering if anybody can point me to some good books on layer 3 switching that gets into technical details on QoS, design, that type of stuff. We are looking at replacing some of our shared 10 Meg equipment with 10/100 switches and we are looking at some layer 3 equipment. I am familiar with routing in routers, but the layer 3 switching stuff is a little different as far as how you design things and so forth. Things are complicated by the fact that we had an Extreme Networks rep come in and convince everybody that you have to have layer 3 switches all the way to the wiring closet, but I don't know enough about layer 3 right now to know if that is true or not so I need to get up to speed on the details of layer 3 and how to best design a layer 3 type network (ex. layer 3 in the core only or all the way out to the wiring closet) so if anybody has any good books on the topic they could point me to I would greatly appreciate it. Thanks. Brian ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching vs. Layer 4 switching?
Layer 4 switching means that a router can forward packets based on L4 information such as TCP port #. This can be used to prioritize specific applications and is currently supported by most vendors. Products from vendors such as Allot, Top Layer and others can even make decisions based on higher level information such as URL. Even more fine grained policy can be enforced using "cookie" switching from vendors such as Arrowpoint (now Cisco), Alteon, Foundry and Extreme (with F5 technology). Irwin -Original Message- From: Ms. Maria [mailto:[EMAIL PROTECTED]] Sent: Wednesday, June 14, 2000 10:58 PM To: [EMAIL PROTECTED] Subject: Layer 3 switching vs. Layer 4 switching? Hi, I was reading Karen Webb book on Building Cisco Multilayer Switched Networks (BCMSN). I came across some information on Layer 4 switching that somehow I didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware based routing that consider the applications. " I understand the Layer 3 switching that is not logical and etc. But what about Layer 4 switching??? What new Switches and Routers are supporting Layer 4 (Transport Layer) switching? If Layer 3 and Layer 4 switching is same than is there any difference? Any responses are welcome on this topic. Thanks for your time! Maria Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Layer 3 switching vs. Layer 4 switching?
On TCP/IP that would mean routing using TCP info (i.e. port number). When using certain apps (voice, for example) it's necessary that the router knows what app is it routing (by using upper layer info) so that it gives apps the service they need. Francisco Muniz "Ms. Maria" <[EMAIL PROTECTED]> escribió en el mensaje de noticias [EMAIL PROTECTED] > Hi, > > I was reading Karen Webb book on Building Cisco Multilayer Switched Networks > (BCMSN). I came across some information on Layer 4 switching that somehow I > didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware > based routing that consider the applications. " > I understand the Layer 3 switching that is not logical and etc. But what > about Layer 4 switching??? What new Switches and Routers are supporting > Layer 4 (Transport Layer) switching? > If Layer 3 and Layer 4 switching is same than is there any difference? > Any responses are welcome on this topic. > > Thanks for your time! > > Maria > > Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com > > ___ > UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html > FAQ, list archives, and subscription info: http://www.groupstudy.com > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > --- ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Layer 3 switching vs. Layer 4 switching?
Hi, I was reading Karen Webb book on Building Cisco Multilayer Switched Networks (BCMSN). I came across some information on Layer 4 switching that somehow I didn't understand. It says that "Layer 4 switches refer to Layer 3 hardware based routing that consider the applications. " I understand the Layer 3 switching that is not logical and etc. But what about Layer 4 switching??? What new Switches and Routers are supporting Layer 4 (Transport Layer) switching? If Layer 3 and Layer 4 switching is same than is there any difference? Any responses are welcome on this topic. Thanks for your time! Maria Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: 6506 Vlan and layer 3 switching question
When you use the MSFC mls rp is automatically configured to the MSFC. The only reason that you would need to enable it is you had disabled it. Check out this link, watch the wrap. http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/ios127xe/config/ mls.htm or http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_5_3/msfc/mls. htm - Original Message - From: "Kent" <[EMAIL PROTECTED]> To: "Michael Rasmussen" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, June 06, 2000 3:28 PM Subject: Re: 6506 Vlan and layer 3 switching question > I understood, you have to configure mls rp for the > mulitlayer swithing to work, right? why you do not > need mls rp when using MSFC? Is that because the RSM > is on board, it automatically does the multilayer > swithing to the MSFC card? > > Thanks > > Kent > --- Michael Rasmussen [EMAIL PROTECTED]> wrote: > > You shouldn't have to do anything else to route > > between just those two VLANs. Also just a side > > note. The mls rp ip command is not necessary since > > you are using the MSFC. > > ""Josh Youngman"" <[EMAIL PROTECTED]> > > wrote in message > > > 002801bfcf35$c2e0$[EMAIL PROTECTED]">news:002801bfcf35$c2e0$[EMAIL PROTECTED]... > > i have a 6506 with a 48prt 10/100 blade i wish to > > configure 6 ports on one subnet (vlan2) and the rest > > on another (Vlan1) and use the supervisor to route > > between the two vlans. does anyone have any sample > > configs on how to do this. so far i have > > created the two vlans and assigned the ports. i > > then did a session 15: > > ! > > router rip > > network 10.0.0.0 > > ! > > Interface vlan1 > > set ip address 10.0.8.21 255.255.252.0 > > mls rp ip > > ! > > interface vlan2 > > set ip add 10.0.12.21 255.255.252.0 > > mls rp ip > > ! > > ! > > > > what else do i need here to route between the two > > vlans? > > > > thanks for any help. > > > > > __ > Do You Yahoo!? > Yahoo! Photos -- now, 100 FREE prints! > http://photos.yahoo.com > ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
