vlan configure

Unanswered Question
Aug 13th, 2007

Hello all,

Can we assign same vlan in different switches in different networks.

eg: vlan 90, 91, 92 assigned for Switch 2 and the same vlan 90, 91, 92 assigned in Switch 3, both switches in different locations & networks this will work out?

Thanks in advance


I have this problem too.
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ycae Mon, 08/13/2007 - 21:40

You have to create a trunk between the 2 switches so that computers from vlan 90 on switch 2 can talk to computers on vlan 90 on switch 3.


ilnaiduccna Mon, 08/13/2007 - 21:55

Hi Yves,

Ok can we create trunk between the 2 switches,

The 2 switches in different locations now can we create trunk in between these, if yes how can you tell what are the commands to create trunk between 2 switches, it may be simple to you but I am new to this things. Plz. kindly give clear information.


ycae Mon, 08/13/2007 - 23:02


Well it is quite simple. Let's assume that you have a 100/fdx port on both switches. Let's assume that the ports are 0/1 for both switches. Interconnect these ports with a cross-over cable. On both switches you can do the following

conf t

interface fastethernet 0/1

switchport mode trunk

Do this on both switches.

You can also create a vtp domain. A vtp domain will help to configure the vlans only on one switch and that the vlans are automaticaly replicated to the second switch.

Let's say on switch 2 you execute the following

vtp domain MyDomain

vtp mode server

on switch 3 you say

vtp domain MyDomain

vtp mode client

Like this any vlan you create on switch 2 will be replicated to switch 3. It is also recommended to only have one server in your vtp domain.

I would suggest to do this in a lab so that you can train yourself a bit and play around with the commands I gave you.

Could you also specify what model of switches you have?


ilnaiduccna Mon, 08/13/2007 - 23:21

Hi Yves,

Thank u for ur explaination, my switch model is 2950

One small doubt that how we can interconnect those ports when both switches in different locations.

Ok you told that with the help of vtp domain whatever the vlan's has created in switch1 the same vlan's will be replicated to switch2 like vlan 90 will as it is replicated in to switch2 as vlan 90.

Just for assume I have assigned vlan 90 for 'core telco nodes' in switch1 and in switch2 vlan 90 assigend for 'data base servers' in this cases is there no confusion?


ycae Mon, 08/13/2007 - 23:45


Well it depends what you mean with different locations.

If you use vtp, vlan 90 will be named the same on both switches. If you don't want to have the core telco nodes to talk with the database servers, than you have to create a new network. Think about vlans like physical networks.

BTW, do you want both switches to talk to each other, or do you just want to know if you can have the same vlans on 2 different switches whcih are not physicaly connected?


ilnaiduccna Tue, 08/14/2007 - 00:44

Hi Yves,

Again thanks,

Yes my both switches are not physicall connected.

Both switches are connected in WAN through E1 and both are in different network like switch1 in 10.104.24.x, switch2 10.105.20.x. As you told if u don't want talk 2 switches need to create a new network am i right? but still both are communicating and accessing each other.

plz. give your response on this.


Edison Ortiz Tue, 08/14/2007 - 13:57

Based on all your replies, yes - this configuration will work since these switches won't be able to see each other via Layer2.

Each switch will keep its Vlan database independently.



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