Stephen, This is getting out of hand, so let me answer your original post based on what I can see from your drawing. First, if you have users in Bldg B that want to communicate with users in Bldg A on the SAME VLAN1, then your "core" L3 switches will see the VLAN ID and switch the packets from ingress to egress ports WITHOUT bothering its Routing table. What you keep referring to as "gateway" is at LAYER 3, i.e. it is only relevant when users in one VLAN needs to communicate OUTSIDE its broadcast domain (aka "subnet" in L3 lingo). And yes, the same VLAN1 traffic will cross your CORE links if that is the only physical link that exists, BUT the traffic gets SWITCHED (much faster) and not routed (much slower). Now, as far as the 3550 switch, all ports are Layer 2 UNTIL you configure "no switchport" which turns the port into a PHYSICAL ROUTED port. This is not the same as a Switched Virtual interface. Once the port is converted into a routed port, you can treat it just like a regular Router port, i.e. run OSPF, BGP, etc.
I hope I've answered your original post. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Stephen Hoover Sent: Monday, February 17, 2003 7:56 PM To: [EMAIL PROTECTED] Subject: Re: Understanding VLANs - how they remove the physical [7:63194] Ok, let me see if I can simply this: A post that Jens Neelsen made says "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." Further he adds "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. " Ok then the question is - if you have a LAN with ALL switches and NO routers - how do you define a gateway on the client? Example: 2 L2 switches. All hosts on switch 1 are in IP subnet 192.168.1.0/24 and all hosts on switch 2 are in IP subnet 192.168.2.0/24. Both L2 switches are connected to a single L3 switch with a router engine in it. Where do you define the gateways at? In order for hosts on L2 switch 1 to communicate with hosts L2 switch 2, the client has to have a gateway to forward to correct?? Stephen ----- Original Message ----- From: "Priscilla Oppenheimer" To: Sent: Monday, February 17, 2003 4:45 PM Subject: RE: Understanding VLANs - how they remove the physical [7:63173] > Stephen Hoover wrote: > > > > back to switch A to get his routing to > > the servers? > > Why would you EVER want a network configured this way?? Or even > > worse, what > > if your respective gateway was 3 or 4 L3 switches away? > > Your gateway can't be any L3 switches (routers) away. It has to be on your > LAN. It has to be in your subnet. It has to be in your broadcast domain. It > has to be in your VLAN. For one thing, a host ARPs for its default gateway. > ARP uses broadcast. > > I just noticed your comment and wanted to add my comment. Without being able > to decode your drawing, it's hard to tell exactly how to answer, but I'm > just trying to get you to think about what really happens to packets on a > campus network. The network design you're considering isn't just > impractical. It won't work, if I understand it correctly. > > Priscilla > > > > > That > > just doesn't > > seem practical to me. > > > > > > Thanks! > > Stephen Hoover > > Dallas, Texas Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=63214&t=63214 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
