Routing a VLAN

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Oct 15th, 2007
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Hi. Im setting up a testbed for routing our voice vlan between 2 switches. Baically what I have are 2 Catalyst express 500's and an 1801 with FE0/0 and FE0/1.

Id Like VLAN 100 (Voice) to exist on both switches (on different networks). This i because we're two companies, and want to run off one phone system, but have separate data.

Id like to, via the router, connect the second switch, on another subnet (separate data vlan) but have our voice vlan visible on that.

How do I go about it?


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ankbhasi Mon, 10/15/2007 - 06:24
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Hi Dav,

I believe it is possible even if you connect the 2 switches together and then connect one switch back to router. And on router you can configure 2 ip address of different subnet on same interface using secondary keyword.

Or else you can also connect your 2 switches to 2 different ports of router and configure 2 different interfaces on router to 2 seperate subnets. Do not configure switchport as trunk ports and normal access ports for vlan 100.

The first solution will save one physical interface on router which are pretty costly. Try any of the 2 and update if that works for you.



davieshuw Mon, 10/15/2007 - 06:40
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Hi there, yes i belive its called routing on a stick. Im wondering if anyone knows what, if any, commands id need to enter on the router for it to 'allow' the VLAN 100 on each switch to talk to each other

ankbhasi Mon, 10/15/2007 - 06:47
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Hi Dav,

What I thaught is not to have router on stick model. Router on stick need us to define vlan encapsulation on router whereas you have only one vlan which is vlan 100 with different subnets.

So you can configure switch port as access port and put it to vlan 100. Connect that port to router fa0/0 and configure 2 ip address something like this

Router(config)#interface fa0/0

Router(config-if)#ip address mask

Router(config-if)#ip address mask secondary

In this way router will route between 2 subnets which exist on same vlan.

You can connect the 2 switches using an access vlan 100 itself if you have only 1 vlan on both the switches which is vlan 100.



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