Showing results for 
Search instead for 
Did you mean: 

VLAN routing between sites

All ,

Here is my scenario.We are moving offices soon. Currently we have connectivity via a laser with 2 2948G switches on each site connected so just a flat network.On new site we have a VOIP solution just installed with 2 4500 L3 switches. Data vlan is vlan 10 and voice is vlan 20. I want to temporarily connect both sites until our MPLS circuits go in so am thinking this.

Present bldg. is on network with no vlans at all. There are 4 backbone 2948g's with STP running between them.New site has network subnets). I cant have the same subnet on 2 different vlans right ?? So I am thinking I need to change everything in present bldg. to be on vlan 10? Will this work and is there anything else I need to take into consideration before I go ahead. Also what commands do i need on CATOS switches. I also need to create vlan on new site switch and make sure spanning tree on current site is spanning to vlan 10 ? I'm sure there is more to do as well.Thanks a lot


You can extend vlan 10 over a trunk link to the old building which has 2948 switches and have that building be part of vlan 10. To do this you will need to configure the port (fiber or copper) that connects between the old and new buildings and trunk vlan 10 and 20 (only if needed).

Also are you gonna run VTP ? If the new building with 4500s already run VTP you should be careful as to adding the 2948s to the network, as VTP and VLAN database info on the VTP server (4500 say) can be affected. Read this link as to caveats that need to be taken care of before adding a new switch to an existing VTP domain.

If you dont want to re-IP the old building, you can do the following.

Run VTP between all the switches in old and new building. Create an additional vlan 30 which extends over a trunk to the old building where the 2948s are. All ports in the 2948s can remain in vlan 30 and 4500 will route the traffic between vlans 10, 20 and 30. This will prevent you from Re-IPing the existing subnet scheme in use at the old building.


PS: Please remember to rate helpful replies!

Sankar Nair
UC Solutions Architect
Pacific Northwest | CDW
CCIE Collaboration #17135 Emeritus