Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Split VLAN over routed backbone

I am attempting to set up a split VLAN over a routed backbone using ethernet connections. I have one router on each segment with 2 VLANs on each segment. I need to know how to set up the IP addressing scheme for the subinterfaces on the routers. I realize that members of the same VLAN have to be on the same subnet, but the configurations I have now are not working.One segment is and the other is


Re: Split VLAN over routed backbone

When you say split, are you trying to configure the same IP subnets at 2 places in the network and use routers to get between them? Thats possible with bridging but isn't clean with routing. It is possible to do this with routing (static host routes, NAT).

Please give us some more details...


New Member

Re: Split VLAN over routed backbone

You may well have to use bridging for this.

A fairly recent feature may also help you - UTI (but only on high end kit currently)

The way I did this was to create on the router's Ethernet port sub interfaces (one per Vlan using ISL) this was connected to a trunk port on a seperate CAT switch where the VLAN's were seperated out. The routers serial interface was configured with frame relay PVC's which were bridged onto the Ethernet's subinterfaces (one per network / PVC).

This allowed me to bridge the Layer 2 networks accros the WAN and extend them to different sites.

I wouldn't recommend this normaly but it helped me get over a migration from ATM LANE issue!

Hope that helps


CreatePlease to create content