Re: Bridge and switch [7:44649]
Marketing! A switch is simply a multiport bridge. Bridges originally had very few ports, as few as two. When hardware became faster and manufacturers started adding more ports to their bridges they started calling them switches to differentiate them from their slower brethren with fewer ports. John >>> "rtiwari" 5/21/02 12:57:01 PM >>> Could somebody will please describe me the difference in between bridge and switch. Thanks Ravi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44651&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
A switch is a multiport bridge. Think of a bridge that bridges together 2 networks (i.e. has two interfaces, one in each network). Then supposed you upgrade to a 3 port bridge, that can connect 3 networks. keep adding ports up to 4, 8, 12, 24, or even 48 and that's a switch. The switch operates pretty much like a bridge where it watches the source MAC addresses in frames, builds a table of MAC addresses and corresponding ports (the CAM table), and forwards broadcasts or traffic destined for a MAC address not in it's CAM table out all ports (except the one it received the frame on) Mike W. "rtiwari" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Could somebody will please describe me the difference in > between bridge and switch. > Thanks > Ravi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44652&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Bridge and switch [7:44649]
A bridge spans a body of water so that two pieces of land can be connected and switch is used to control the flow of electricityJust kidding! Try this link (watch for wrap)!: http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/bridging.htm Shawn K. -Original Message- From: rtiwari [mailto:[EMAIL PROTECTED]] Sent: Tuesday, May 21, 2002 2:57 PM To: [EMAIL PROTECTED] Subject: Bridge and switch [7:44649] Could somebody will please describe me the difference in between bridge and switch. Thanks Ravi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44654&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
Switching is a marketing term. You would be wise to focus on Bridging and Routing and when the word switch appears, read to fine print to figure out if the device in question bridges or routes. At 02:57 PM 5/21/2002 -0400, rtiwari wrote: >Could somebody will please describe me the difference in >between bridge and switch. >Thanks >Ravi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44655&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
ideally when during evalution there was a need for a device to interconnect two networks and bridges came into existence which let two segments to be connected, so that alfi in accounts can send messages to rita in marketing. when the greedy boss extended the company he bought in many computers and users segments started growing and the evalution commanded the need for a switch, a multi port bridge later when the greedy boss starting expaning to many cities rotuers were born to interconnect the offices :) sen - Quoting rtiwari : > Could somebody will please describe me the difference in > between bridge and switch. > Thanks > Ravi cheers - sen Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44656&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
Switch = mega interfaced bridge. Dave rtiwari wrote: > > Could somebody will please describe me the difference in > between bridge and switch. > Thanks > Ravi -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 "Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44658&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Bridge and switch [7:44649]
John and Mike are both right. As a matter of fact, there are several definitions. In my opinion, the whole topic is adequately described in Interconnections, by Radia Perlman. Her take (in a nutshell) is that they are technically one in the same and that the difference is marketing terminology. Ethernet switches are essentially multi-port transparent bridges (but what bridge isn't 2 ports or more?). A Ethernet switch or bridge with only 2 ports could be called a switch or bridge depending on which one is a better market term. As time has evolved, new functionality has been introduced into Ethernet switches, but at their base functionality, it's all pretty much the same. -Original Message- From: Michael L. Williams [mailto:[EMAIL PROTECTED]] Sent: Tuesday, May 21, 2002 3:20 PM To: [EMAIL PROTECTED] Subject: Re: Bridge and switch [7:44649] A switch is a multiport bridge. Think of a bridge that bridges together 2 networks (i.e. has two interfaces, one in each network). Then supposed you upgrade to a 3 port bridge, that can connect 3 networks. keep adding ports up to 4, 8, 12, 24, or even 48 and that's a switch. The switch operates pretty much like a bridge where it watches the source MAC addresses in frames, builds a table of MAC addresses and corresponding ports (the CAM table), and forwards broadcasts or traffic destined for a MAC address not in it's CAM table out all ports (except the one it received the frame on) Mike W. "rtiwari" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Could somebody will please describe me the difference in > between bridge and switch. > Thanks > Ravi Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44660&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
This begs the question, what is the difference between a multi-port bridge and a switch? Or, what is a switch when it routes? I personally think bridge and router convey with relatively little ambiguity the function of a device whereas switch is simply a tool that marketing folks use when they need to reverse their previous opinion on devices. IE, after telling folks routers are better than bridges for a few years (in order to sell routers), when it becomes more lucrative to sell bridges again, one can simply call the bridge a switch and superficially maintains ones integrity. Furthermore, when it becomes more lucrative to sell routers again, one can simply call the router a layer 3 switch and again perform the switchback without visibly contradicting ones previous assertion. I think the chain looks something like this bridges -> routers -> switches - > l3 switches -> etc etc At 04:02 PM 5/21/2002 -0400, MADMAN wrote: >Switch = mega interfaced bridge. > > Dave > >rtiwari wrote: > > > > Could somebody will please describe me the difference in > > between bridge and switch. > > Thanks > > Ravi >-- >David Madland >Sr. Network Engineer >CCIE# 2016 >Qwest Communications Int. Inc. >[EMAIL PROTECTED] >612-664-3367 > >"Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44665&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
is it good to say that Bridge supports up to 16 ports ans is software based. but Switch supports any number od ports and is hardware based. Peter van Oene wrote: > This begs the question, what is the difference between a multi-port bridge > and a switch? Or, what is a switch when it routes? I personally think > bridge and router convey with relatively little ambiguity the function of a > device whereas switch is simply a tool that marketing folks use when they > need to reverse their previous opinion on devices. IE, after telling folks > routers are better than bridges for a few years (in order to sell routers), > when it becomes more lucrative to sell bridges again, one can simply call > the bridge a switch and superficially maintains ones > integrity. Furthermore, when it becomes more lucrative to sell routers > again, one can simply call the router a layer 3 switch and again perform > the switchback without visibly contradicting ones previous assertion. I > think the chain looks something like this > > bridges -> routers -> switches - > l3 switches -> etc etc > > > > At 04:02 PM 5/21/2002 -0400, MADMAN wrote: > >>Switch = mega interfaced bridge. >> >> Dave >> >>rtiwari wrote: >> >>>Could somebody will please describe me the difference in >>>between bridge and switch. >>>Thanks >>>Ravi >>> >>-- >>David Madland >>Sr. Network Engineer >>CCIE# 2016 >>Qwest Communications Int. Inc. >>[EMAIL PROTECTED] >>612-664-3367 >> >>"Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44666&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
ditto, you won't get an argument from me!!! Peter van Oene wrote: > > This begs the question, what is the difference between a multi-port bridge > and a switch? Or, what is a switch when it routes? I personally think > bridge and router convey with relatively little ambiguity the function of a > device whereas switch is simply a tool that marketing folks use when they > need to reverse their previous opinion on devices. IE, after telling folks > routers are better than bridges for a few years (in order to sell routers), > when it becomes more lucrative to sell bridges again, one can simply call > the bridge a switch and superficially maintains ones > integrity. Furthermore, when it becomes more lucrative to sell routers > again, one can simply call the router a layer 3 switch and again perform > the switchback without visibly contradicting ones previous assertion. I > think the chain looks something like this > > bridges -> routers -> switches - > l3 switches -> etc etc > > At 04:02 PM 5/21/2002 -0400, MADMAN wrote: > >Switch = mega interfaced bridge. > > > > Dave > > > >rtiwari wrote: > > > > > > Could somebody will please describe me the difference in > > > between bridge and switch. > > > Thanks > > > Ravi > >-- > >David Madland > >Sr. Network Engineer > >CCIE# 2016 > >Qwest Communications Int. Inc. > >[EMAIL PROTECTED] > >612-664-3367 > > > >"Emotion should reflect reason not guide it" -- David Madland Sr. Network Engineer CCIE# 2016 Qwest Communications Int. Inc. [EMAIL PROTECTED] 612-664-3367 "Emotion should reflect reason not guide it" Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44669&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
And it's worth mentioning a couple other things too, just to confuse matters. ;-) Although a switch behaves like a multiport bridge, it is often placed in a topology where a hub used to go. Because a switch has so many ports, people use them to connect individual stations. Bridges were rarely used that way. Bridges connect networks. A switch can forward multiple frames at once, whereas many bridges couldn't. Due to the advanced "switching fabric" (to use another marketing term), a switch can forward a frame from port 1 to port 2 while at the same time forwarding a frame form port 3 to port 4, for example. Switch design is much more complex than bridge design. Bridges (and first generation switches) had a shared bus and very few bells and whistles. Modern switches use technologies such as ASICs shared memory crosspoint (crossbar) architectures star-wired architectures methods to eliminate head of the line blocking virtual output queuing etc. You get the idea. Priscilla At 03:19 PM 5/21/02, John Neiberger wrote: >Marketing! A switch is simply a multiport bridge. Bridges originally >had very few ports, as few as two. When hardware became faster and >manufacturers started adding more ports to their bridges they started >calling them switches to differentiate them from their slower brethren >with fewer ports. > >John > > >>> "rtiwari" 5/21/02 12:57:01 PM >>> >Could somebody will please describe me the difference in >between bridge and switch. >Thanks >Ravi Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44679&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
At 05:11 PM 5/21/02, rtiwari wrote: >is it good to say that >Bridge supports up to 16 ports ans is software based. No, I think the discriminator is 15 ports. Just KIDDING! Seriously, assigning a number is not necessary. Most bridges had just two ports, but there probably were a few vendors that had bridges with a few more ports. Most bridges were hardware based. Well, there was that irksome bridge software for the IBM PC that turned it into a source-routing bridge. Throw two NICs into an old PC, run that software, and you could extend your network. Caused all sorts of problems if the PC was underpowered. ;-) Switches have more sophisticated hardware and numerous ports. That's really about all you can say (other than the "it's marketing" answer and my more detailed answer about "switching fabrics.") >but Switch supports any number od ports and is >hardware based. > > > > > >Peter van Oene wrote: > > > This begs the question, what is the difference between a multi-port bridge > > and a switch? Or, what is a switch when it routes? I personally think > > bridge and router convey with relatively little ambiguity the function of >a > > device whereas switch is simply a tool that marketing folks use when they > > need to reverse their previous opinion on devices. IE, after telling >folks > > routers are better than bridges for a few years (in order to sell >routers), > > when it becomes more lucrative to sell bridges again, one can simply call > > the bridge a switch and superficially maintains ones > > integrity. Furthermore, when it becomes more lucrative to sell routers > > again, one can simply call the router a layer 3 switch and again perform > > the switchback without visibly contradicting ones previous assertion. I > > think the chain looks something like this > > > > bridges -> routers -> switches - > l3 switches -> etc etc > > > > > > > > At 04:02 PM 5/21/2002 -0400, MADMAN wrote: > > > >>Switch = mega interfaced bridge. > >> > >> Dave > >> > >>rtiwari wrote: > >> > >>>Could somebody will please describe me the difference in > >>>between bridge and switch. > >>>Thanks > >>>Ravi > >>> > >>-- > >>David Madland > >>Sr. Network Engineer > >>CCIE# 2016 > >>Qwest Communications Int. Inc. > >>[EMAIL PROTECTED] > >>612-664-3367 > >> > >>"Emotion should reflect reason not guide it" Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44680&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
I was under the impression that, while a switch is often termed a multiport bridge, there is one fundamental difference in the way the two devices forward frames. While my source is not always the most credible or reliable (Course Technology Networks Plus book), it does cause me to stop and think for a minute. Anyway, the difference (as described in the book) is as follows: If a multiport bridge determines (based on the destination MAC address) that the destination node is on another subnet, it will broadcast the frame out all ports except the originating port. A switch, on the other hand, is smart enough to only forward the frame out the destination port. Both devices handle unknown frames and broadcasts the same way, ie. they will forward the packets out all ports except the one the frame was received on. Any thoughts? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44736&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
There are a few things wrong with that description. First, switches and/or bridges are layer two devices and wouldn't be aware of different IP subnets in the first place. A switch or bridge will forward a frame out all ports except the originating port if it has not yet learned the correct port for the destination. It has nothing to do with subnets whatsoever. A switch is nothing more than a marketing term for a bridge on steroids. From a layer two perspective there is no difference in their operation. This entire thread seems analagous to arguing that a square is not a rectangle. I can see it now... " Originally all we had were rectangles but when we offered a slightly different rectangle we decided to call it a square to differentiate it from the previous rectangles. However, it's still a rectangle when you get right down to it." >>> "Kevin Jones" 5/22/02 12:58:37 PM >>> I was under the impression that, while a switch is often termed a multiport bridge, there is one fundamental difference in the way the two devices forward frames. While my source is not always the most credible or reliable (Course Technology Networks Plus book), it does cause me to stop and think for a minute. Anyway, the difference (as described in the book) is as follows: If a multiport bridge determines (based on the destination MAC address) that the destination node is on another subnet, it will broadcast the frame out all ports except the originating port. A switch, on the other hand, is smart enough to only forward the frame out the destination port. Both devices handle unknown frames and broadcasts the same way, ie. they will forward the packets out all ports except the one the frame was received on. Any thoughts? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44741&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
At 02:58 PM 5/22/02, Kevin Jones wrote: >If a multiport bridge determines (based on the destination MAC address) that >the destination node is on another subnet, Stop right there. It can't figure out that the destination is on a different subnet from the MAC address. Subnets are differentiated by network-layer information. MAC addresses are at the data-link layer. If the destination is on a different subnet, the destination MAC will be a router's MAC address, although the bridge (switch) wouldn't recognize that (unless it had some weird feature that did this, which is unlikely). If the bridge (switch) has learned which port reaches that MAC address, then it will forward the frame out that port and no other. If it hasn't learned how to reach that address yet, then it will flood the frame out all ports. Bridges and switches behave exactly the same. Priscilla > it will broadcast the frame out >all ports except the originating port. A switch, on the other hand, is >smart enough to only forward the frame out the destination port. Both >devices handle unknown frames and broadcasts the same way, ie. they will >forward the packets out all ports except the one the frame was received on. > >Any thoughts? Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44753&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
"John Neiberger" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > However, > it's still a rectangle when you get right down to it." Hey. A square isn't a rectangle!!! (just kidding I just thought I'd be stubborn... hehe) Good analogy.. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44758&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
I was oblivious to the fact that I was using the word "subnet". What I should have used is the word "segment". Anyway, I went back to what I thought was the source and was unable to find the description I had read. I'll look again. Not sure where I read it now. Anyway, this thread has confirmed what I have always understood, ie. that switches are multiport bridges. If I find that description again, I'll post it here for you to take a look at. ""Priscilla Oppenheimer"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > At 02:58 PM 5/22/02, Kevin Jones wrote: > >If a multiport bridge determines (based on the destination MAC address) that > >the destination node is on another subnet, > > Stop right there. It can't figure out that the destination is on a > different subnet from the MAC address. Subnets are differentiated by > network-layer information. MAC addresses are at the data-link layer. > > If the destination is on a different subnet, the destination MAC will be a > router's MAC address, although the bridge (switch) wouldn't recognize that > (unless it had some weird feature that did this, which is unlikely). If the > bridge (switch) has learned which port reaches that MAC address, then it > will forward the frame out that port and no other. If it hasn't learned how > to reach that address yet, then it will flood the frame out all ports. > > Bridges and switches behave exactly the same. > > Priscilla > > > > > it will broadcast the frame out > >all ports except the originating port. A switch, on the other hand, is > >smart enough to only forward the frame out the destination port. Both > >devices handle unknown frames and broadcasts the same way, ie. they will > >forward the packets out all ports except the one the frame was received on. > > > >Any thoughts? > > > Priscilla Oppenheimer > http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44759&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
At 06:11 PM 5/22/02, Kevin Jones wrote: >I was oblivious to the fact that I was using the word "subnet". What I >should have used is the word "segment". Ah. That makes more sense. When a frame arrives, both bridges and switches send the frame on its way without sending it back onto the originating segment. If the bridge (switch) has learned which specific port to use, it sends the frame out just that port. If it hasn't learned yet, then it floods it out all ports except the originating port. That's the "unknown frames" that you mentioned in the first message. (It means "unknown destination," as in not knowing which port to use.) You get the picture, I'm sure, but it's still good to clarify the concepts. Priscilla >Anyway, I went back to what I >thought was the source and was unable to find the description I had read. >I'll look again. Not sure where I read it now. Anyway, this thread has >confirmed what I have always understood, ie. that switches are multiport >bridges. If I find that description again, I'll post it here for you to >take a look at. > > >""Priscilla Oppenheimer"" wrote in message >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > At 02:58 PM 5/22/02, Kevin Jones wrote: > > >If a multiport bridge determines (based on the destination MAC address) >that > > >the destination node is on another subnet, > > > > Stop right there. It can't figure out that the destination is on a > > different subnet from the MAC address. Subnets are differentiated by > > network-layer information. MAC addresses are at the data-link layer. > > > > If the destination is on a different subnet, the destination MAC will be a > > router's MAC address, although the bridge (switch) wouldn't recognize that > > (unless it had some weird feature that did this, which is unlikely). If >the > > bridge (switch) has learned which port reaches that MAC address, then it > > will forward the frame out that port and no other. If it hasn't learned >how > > to reach that address yet, then it will flood the frame out all ports. > > > > Bridges and switches behave exactly the same. > > > > Priscilla > > > > > > > > > it will broadcast the frame out > > >all ports except the originating port. A switch, on the other hand, is > > >smart enough to only forward the frame out the destination port. Both > > >devices handle unknown frames and broadcasts the same way, ie. they will > > >forward the packets out all ports except the one the frame was received >on. > > > > > >Any thoughts? > > > > > > Priscilla Oppenheimer > > http://www.priscilla.com Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44765&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Bridge and switch [7:44649]
If you substitute the word "segment" where they have "subnet" then I'd be happy with the description. I've seen others use the two terms to mean the same thing, I suppose you could argue it both ways. In my mind, "segment" = L2; "subnet" = L3. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Kevin Jones Sent: Wednesday, May 22, 2002 1:59 PM To: [EMAIL PROTECTED] Subject: Re: Bridge and switch [7:44649] I was under the impression that, while a switch is often termed a multiport bridge, there is one fundamental difference in the way the two devices forward frames. While my source is not always the most credible or reliable (Course Technology Networks Plus book), it does cause me to stop and think for a minute. Anyway, the difference (as described in the book) is as follows: If a multiport bridge determines (based on the destination MAC address) that the destination node is on another subnet, it will broadcast the frame out all ports except the originating port. A switch, on the other hand, is smart enough to only forward the frame out the destination port. Both devices handle unknown frames and broadcasts the same way, ie. they will forward the packets out all ports except the one the frame was received on. Any thoughts? Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44806&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
Ok. I found the source of the information. I would like to here your feedback on this. Course Technology * Thompson Learning, i-Net+ Guide to Internet Technologies, Jean Andrews, p. 443-445 "What is the difference between a bridge and a switch? The main difference is how they work. A bridge broadcasts data to one or more LANs while a switch knows which LAN a packet should be sent to." "In order to determine which network the packet should be sent to, the bridge creates and maintains a routing table that lists the computers on each LAN. A separate table is kept for each LAN. When a data packet reaches the bridge, the bridge looks at the packet's destination address, then searches the routing table for the originating LAN, looking for the destination address of the data packet. If it finds the address in this routing table, it drops the packet, knowing that the packet will have already reached its destination, because it was broadcast to all nodes on the LAN by the LAN's hub." "If the bridge did not find the destination address in the routing table for that LAN, it broadcasts the packet to all nodes on all LANs it is connected to except the LAN that the packet came from. Therefore, a bridge only makes a single decision, 'Is this packet destined for a node on its own network?' If the answer is 'No,', then the bridge simply broadcasts it to all other LANs." "A switch, on the other hand, deosn not work by sending broadcast messages. Just like bridges, switches also keep tables of all the MAC addresses of all the devices connected to the switch. They use these tables to determine which path to use when sending packets." "... Using the destination address in the header of the packet, the switch would refer to its tables and determine the LAN to which the packet is addressed. The switch then forwards the packet to the proper LAN, rather than broadcasting the packet to all the LANs." >From this thread, and from past experience, shall we assume that this is completely false? While i-Net plus only skims the surface of network technology, this book (like many others) seems to have a lot of errors. Another example would be the fact that the MAC tables are referred to as routing tables. That reminds me, what is the difference between a MAC table and a CAM table? Kevin Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44951&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
I used to wonder why I had such a hard time grasping technology concepts until I reached a level where I actually understood some of this stuff. Then I found that a lot of sources either did not understand the concepts themselves or worse yet, they were so imprecise with their language and terminology, that they created confusion in the mind of the newbie learner. Some comments below: ""Kevin Jones"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Ok. I found the source of the information. I would like to here your > feedback on this. > > Course Technology * Thompson Learning, i-Net+ Guide to Internet > Technologies, Jean Andrews, p. 443-445 > > "What is the difference between a bridge and a switch? The main difference > is how they work. A bridge broadcasts data to one or more LANs while a > switch knows which LAN a packet should be sent to." ? since both are layer 2 devices, and layer two has no concept of "LAN" let alone "different LAN's" what does this mean? > > "In order to determine which network the packet should be sent to, the > bridge creates and maintains a routing table that lists the computers on The use of the term "routing table" is inaacurate. layer two does not "route" I believe the proper term is "forwarding base", which is more generic, and more proper. > each LAN. A separate table is kept for each LAN. ?? not on any bridge or switch I've ever worked with >When a data packet > reaches the bridge, the bridge looks at the packet's destination address, > then searches the routing table for the originating LAN, looking for the > destination address of the data packet. If it finds the address in this > routing table, it drops the packet, knowing that the packet will have > already reached its destination, because it was broadcast to all nodes on > the LAN by the LAN's hub." sigh. totally wrong in concept and in explaination... > > "If the bridge did not find the destination address in the routing table for > that LAN, it broadcasts the packet to all nodes on all LANs it is connected > to except the LAN that the packet came from. Therefore, a bridge only makes > a single decision, 'Is this packet destined for a node on its own network?' > If the answer is 'No,', then the bridge simply broadcasts it to all other > LANs." ??. I think I begin to understand what the author is intending. The author appears to be saying that each port on a bridge is associated with a LAN. This can be considered conceptually correct in a manner of speaking, but again, the imprecision of terminology is causing confusion.. > > "A switch, on the other hand, deosn not work by sending broadcast messages. > Just like bridges, switches also keep tables of all the MAC addresses of all > the devices connected to the switch. They use these tables to determine > which path to use when sending packets." here we go,,, the author now gets into the correct concept - MAC addresses - which bridges use also. > > "... Using the destination address in the header of the packet, the switch > would refer to its tables and determine the LAN to which the packet is > addressed. The switch then forwards the packet to the proper LAN, rather > than broadcasting the packet to all the LANs." the author continues to confuse L2 and L3 terminaology. L2 is "frame" - recall your CCNA materials. > > From this thread, and from past experience, shall we assume that this is > completely false? While i-Net plus only skims the surface of network > technology, this book (like many others) seems to have a lot of errors. > Another example would be the fact that the MAC tables are referred to as > routing tables. no kidding there are errors. just goes to show > > That reminds me, what is the difference between a MAC table and a CAM table? Cisco calls the mac table a "content addressable memory" table. without spending more time than I have at the moment, I can't find a history on CCO as to why they do this. > > Kevin Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44960&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
Both bridges and switches learn the port to use to reach a MAC destination. If they haven't learned it yet, they flood the frame out all ports except the originating port. Jean Andrews has written some superb books on PC technology. I have a book by her called "A+ Guide to Managing and Maintaining Your PC" that is excellent. But she should stick to her day job. She doesn't seem to know networking. Her description of bridges and switches is false, as you say. Maybe she could write some fiction in her spare time. ;-) The only real difference between bridges and switches is in their architectures, both hardware and software. Switches have more ports. Switches have a more complex switching fabric that lets them forward multiple frames at once. They are often implemented as a crossbar. Think of a bridge as being like a literal bridge across a river or whatever. Think of a switch as being like a complicated Japanese Pachinko machine! Regarding the difference between a MAC table and CAM table: They are just different names for the same thing. Priscilla At 10:57 AM 5/24/02, Kevin Jones wrote: >Ok. I found the source of the information. I would like to here your >feedback on this. > >Course Technology * Thompson Learning, i-Net+ Guide to Internet >Technologies, Jean Andrews, p. 443-445 > >"What is the difference between a bridge and a switch? The main difference >is how they work. A bridge broadcasts data to one or more LANs while a >switch knows which LAN a packet should be sent to." > >"In order to determine which network the packet should be sent to, the >bridge creates and maintains a routing table that lists the computers on >each LAN. A separate table is kept for each LAN. When a data packet >reaches the bridge, the bridge looks at the packet's destination address, >then searches the routing table for the originating LAN, looking for the >destination address of the data packet. If it finds the address in this >routing table, it drops the packet, knowing that the packet will have >already reached its destination, because it was broadcast to all nodes on >the LAN by the LAN's hub." > >"If the bridge did not find the destination address in the routing table for >that LAN, it broadcasts the packet to all nodes on all LANs it is connected >to except the LAN that the packet came from. Therefore, a bridge only makes >a single decision, 'Is this packet destined for a node on its own network?' >If the answer is 'No,', then the bridge simply broadcasts it to all other >LANs." > >"A switch, on the other hand, deosn not work by sending broadcast messages. >Just like bridges, switches also keep tables of all the MAC addresses of all >the devices connected to the switch. They use these tables to determine >which path to use when sending packets." > >"... Using the destination address in the header of the packet, the switch >would refer to its tables and determine the LAN to which the packet is >addressed. The switch then forwards the packet to the proper LAN, rather >than broadcasting the packet to all the LANs." > > From this thread, and from past experience, shall we assume that this is >completely false? While i-Net plus only skims the surface of network >technology, this book (like many others) seems to have a lot of errors. >Another example would be the fact that the MAC tables are referred to as >routing tables. > >That reminds me, what is the difference between a MAC table and a CAM table? > >Kevin Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44974&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
First let me say that I was looking for a book to recommend to a friend, and I picked up this same book in the store and thumbed through I actually happen to stop on the part where it talked about how a switch (bridge) builds a routing table etc... I put the book down, pointed at it, and told my friend "Don't by this book!" I am appalled at what passes for techincal books (I guess I'm more sensitive about networking topics). but in the technical field, one must be careful about the terms they use because they can mean different things. packet -vs- frame, etc. > Cisco calls the mac table a "content addressable memory" table. without > spending more time than I have at the moment, I can't find a history on CCO > as to why they do this. Here is some info I found on CAM... basically, you can use the data to find itself in memory (as opposed to having to know it's address in memory).. (all of the following info is from various web pages found through Google) Content-Addressable Memory (CAM): In this information-handling model, each possible piece of information has one and only one possible storage location. The data is its own key. It is important to differentiate CAM from a hash key or traditional index. With conventional indexing schemes the data content is used with a hash or index to produce the address location of the data. The address has no real or direct relationship with the information contained in the data. With CAM, the data describes its own storage location. This also means all like data will always be found close together in the physical data structure. There is a direct relationship between the information in the data and its location in the physical data store. In a symbolic system information is stored in an external mechanism. In the example of the computer it is stored in files on the disks. As the information has been encoded in some form of file system in order to retrieve that information one must know the index system of the files. In other words, data can only be accessed by certain attributes. In a connectionist system the data is stored in the activation pattern of the units. Hence, if a processing unit receives excitatory input from one of its connections, each of its other connections will either be excited or inhibited. If these connections represent the attributes of the data then the data may be recalled by any one of its attributes, not just those that are part of an indexing system. As these connections represent the content of the data, this type of memory is called content addressable memory. This type of memory has the advantage of allowing greater flexibility of recall and is more robust. You can compare CAM to the inverse of RAM. When read, RAM produces the data for a given address. Conversely, CAM produces an address for a given data word. When searching for data within a RAM block, the search is performed serially. Thus, finding a particular data word can take many cycles. CAM searches all addresses in parallel and produces the address storing a particular word. You can use CAM for any application requiring high-speed searches, such as networking, communications, data compression, and cache management. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44997&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
"Priscilla Oppenheimer" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Regarding the difference between a MAC table and CAM table: They are just > different names for the same thing. One small quibble (heheh. don't you expect this from me by now =) Although they do essentially refer to the same thing (a table of MAC addresses) (I know you know this, Priscilla, I'm just pointing out for others), the table of MAC addresses kept by a switch (in Cisco switches, I can't speak for other vendors) is stored in a type of memory, CAM memory, which is different than RAM and operates using a different mechanism (see my other recent post in this thread).. so, although we commonly refer to it as the CAM table (and as good Cisco network people we should cuz that's what Cisco calls it) we're really referring to is the table of MAC addresses that happen to be stored in CAM memory.. Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=44998&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
first of all, thanks for the research. it makes sense now that I've read through it. it appears that things have changed a lot since the days of ISAM/VSAM and hashed lookups. I recall reading a bit about CEF, and coming to a similar conclusion - that the Computer Science people have done extensive research and made substantial improvements to table lookup algorithms. one more reason why I love this newsgroup. ""Michael L. Williams"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > First let me say that I was looking for a book to recommend to a friend, and > I picked up this same book in the store and thumbed through I actually > happen to stop on the part where it talked about how a switch (bridge) > builds a routing table etc... I put the book down, pointed at it, and > told my friend "Don't by this book!" I am appalled at what passes for > techincal books (I guess I'm more sensitive about networking topics). > but in the technical field, one must be careful about the terms they use > because they can mean different things. packet -vs- frame, etc. > > > Cisco calls the mac table a "content addressable memory" table. without > > spending more time than I have at the moment, I can't find a history on > CCO > > as to why they do this. > > Here is some info I found on CAM... basically, you can use the data to > find itself in memory (as opposed to having to know it's address in > memory).. (all of the following info is from various web pages found > through Google) > > Content-Addressable Memory (CAM): In this information-handling model, each > possible piece of information has one and only one possible storage > location. The data is its own key. It is important to differentiate CAM from > a hash key or traditional index. With conventional indexing schemes the > data content is used with a hash or index to produce the address location of > the data. The address has no real or direct relationship with the > information contained in the data. With CAM, the data describes its own > storage location. This also means all like data will always be found close > together in the physical data structure. There is a direct relationship > between the information in the data and its location in the physical data > store. > > In a symbolic system information is stored in an external mechanism. In the > example of the computer it is stored in files on the disks. As the > information has been encoded in some form of file system in order to > retrieve that information one must know the index system of the files. In > other words, data can only be accessed by certain attributes. In a > connectionist system the data is stored in the activation pattern of the > units. Hence, if a processing unit receives excitatory input from one of its > connections, each of its other connections will either be excited or > inhibited. If these connections represent the attributes of the data then > the data may be recalled by any one of its attributes, not just those that > are part of an indexing system. As these connections represent the content > of the data, this type of memory is called content addressable memory. This > type of memory has the advantage of allowing greater flexibility of recall > and is more robust. > > You can compare CAM to the inverse of RAM. When read, RAM produces the data > for a given address. Conversely, CAM produces an address for a given data > word. When searching for data within a RAM block, the search is performed > serially. Thus, finding a particular data word can take many cycles. CAM > searches all addresses in parallel and produces the address storing a > particular word. You can use CAM for any application requiring high-speed > searches, such as networking, communications, data compression, and cache > management. > > Mike W. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=45035&t=44649 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Bridge and switch [7:44649]
""Michael L. Williams"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... snip a bit > builds a routing table etc... I put the book down, pointed at it, and > told my friend "Don't by this book!" I am appalled at what passes for > techincal books (I guess I'm more sensitive about networking topics). > but in the technical field, one must be careful about the terms they use > because they can mean different things. packet -vs- frame, etc. CL: having done a few technical reviews for various levels of publication now, I have a comment or two. Some publishers are better than others, but all are under severe pressure to get books to market, to cut the time from initial proposal to distribution to the absolute minimum. CL: There was one publisher who expected me to turn things around on a dime. The editor with whom I worked was furious that it took me more than an hour to rubber stamp what the author had written. The attitude certainly explains some of the idiot mistakes in a series of books by someone whom all of us on this list have used with great success in our certification pursuits. CL: there was another publisher who contracted me at the absolute last minute, and when I returned my review with a list of errors I had found, told me that it didn't matter - the work had already gone to press. that since this was for CCIE level certification, it would be a good exercise for the CCIE candidates to discover the errors for themselves. CL: I'm currently reviewing a book for a publisher who seems to appreciate my efforts to be thorough, and with an author who takes criticism well. As a result, when the book is published you will not be reading about how GRE is used in conjunction with L2TP to create secure VPN tunnels. Nor will you be reading what amounts to incomprehensible gibberish in certain places. The author knows his stuff in certain areas, but is unsure in other areas. The point being that the author wants to write a good book, and is willing to take avice on how to improve his writing, and the publisher wants a good book and is willing to accept that it takes a bit more time to create one. CL: Based on previous experience, I think it is safe to say that these attitudes are the exception, and not the rule. > > > Cisco calls the mac table a "content addressable memory" table. without > > spending more time than I have at the moment, I can't find a history on > CCO > > as to why they do this. > > Here is some info I found on CAM... basically, you can use the data to > find itself in memory (as opposed to having to know it's address in > memory).. (all of the following info is from various web pages found > through Google) > > Content-Addressable Memory (CAM): In this information-handling model, each > possible piece of information has one and only one possible storage > location. The data is its own key. It is important to differentiate CAM from > a hash key or traditional index. With conventional indexing schemes the > data content is used with a hash or index to produce the address location of > the data. The address has no real or direct relationship with the > information contained in the data. With CAM, the data describes its own > storage location. This also means all like data will always be found close > together in the physical data structure. There is a direct relationship > between the information in the data and its location in the physical data > store. > > In a symbolic system information is stored in an external mechanism. In the > example of the computer it is stored in files on the disks. As the > information has been encoded in some form of file system in order to > retrieve that information one must know the index system of the files. In > other words, data can only be accessed by certain attributes. In a > connectionist system the data is stored in the activation pattern of the > units. Hence, if a processing unit receives excitatory input from one of its > connections, each of its other connections will either be excited or > inhibited. If these connections represent the attributes of the data then > the data may be recalled by any one of its attributes, not just those that > are part of an indexing system. As these connections represent the content > of the data, this type of memory is called content addressable memory. This > type of memory has the advantage of allowing greater flexibility of recall > and is more robust. > > You can compare CAM to the inverse of RAM. When read, RAM produces the data > for a given address. Conversely, CAM produces an address for a given data > word. When searching for data within a RAM block, the search is performed > serially. Thus, finding a particular data word can take many cycles. CAM > searches all addresses in parallel and produces the address storing a > particular word. You can use CAM for any application requiring high-speed > searches, such as networking, communications, data compressio
