VLAN routing on Catalyst plus external WAN router issue......

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Mar 9th, 2006
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Bit of advice if possible.

I've got a project to implement VLAN's on a MAN, which is easy enough, using CAT4506 and a mixture of 3750 and 2950 switches. The Vlan aspect is OK but I'm a bit unsure as to how to integrate the WAN into the design.

I have two core WAN access sites each with 2 * cat4506 switches of which one at each site attach to a WAN router (3725)

The CAT4506 switches will be doing the vlan routing but the 3725 routers (one at each site in a HSRP group) will be routing the WAN. Obviously these need to be attached to the catalysts for WAN access. As I have seperate routers for vlan routing and wan routing, what is the best way to configure this ?????

Is configuring a seperate VLAN for the routers the best idea ? or is it best to use the sub interface option on the router ethernet ports ?

Do I just use a static route of last resort on the Catalyst pointing to the routers ?

Help :-)

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lgijssel Thu, 03/09/2006 - 06:56
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When you arte still in the design-phase, I want to strongly discourage you from designing a network with vlans that span multiple sites.

You will always run int STP issues in one way or another. The following link will give some sensible information on this subject:


I hope that it will point you to the right (or at leats an optimal) solution for your specific design.



hullmackem Fri, 03/10/2006 - 03:47
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Yes true, the vlans are only buildings wide not MAN wide. The main problem is the integration of the routers and layer 3 switches.

Thanksfor the help though.


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