Layer 2 traffic over a Layer 3 link?

dan102877 · ‎01-24-2005

I have a 6500(ios) on one side, and a 6500(ios) on another side. They are connected via a routed fiber link. Is it possible to send the layer 2 VLAN traffic from one 6500 to the other over same routed link without hooking up a seperate layer 2 link? And the same VLAN needs to reside on both 6500's. for example, VLAN 200 needs to reside on both 6500's.

ehirsel · ‎01-24-2005

I don't believe that there is. If there is a way, you will have to configure HSRP or some other protocol to advertise which 6509 will have the routed interface active to handle that vlan. It will make a difficult config to maintain and manage on both 6500 units.

Unless there is a need for the two vlans to connect at layer 2, I would recommend that you route between the 6500s like you currently do. That is use separate vlans with seperate subnets. If you are worried about security of the traffic, you can create an IPSEC vpn.

Let me know if this was of help.

mfowler · ‎01-25-2005

You will need a trunk for the traffic to flow and you can set up a trunk with a layer 3 link. All that need to be setup on both ends is for the vlans to match and it should pass the data.

scottmac · ‎01-25-2005

This is where a Bridged Virtual Interface (BVI) might come in handy.

The two interfaces on the "middle" router would be bridged to each other (maintaining your VLAN / L2 traffic), and the pair of bridged interfaces would route to the other interfaces on the system.

Think of it as a "T" where the top crossbar is the bridged interfaces, and the decender is the routed connection. Any traffic on the bridged interfaces stay in the VLAN / broadcast domain they represent, any traffic needing to exit the VLAN / broadcast domain would be handled as routed traffic to / through another interface.

Check it out. Do a search on the main site for configuration examples and more detailed info.

FWIW

Scott

jroyster · ‎01-26-2005

I'm thinking tunnel.

Setup a tunnel between the 6500s over the routed link and then bridge over it.

Just be careful with bridging as you're sending all your broadcasts/multicasts as well. There may be some layer3 trunking that you can use but I can't think of it off the top of my head, like 802.1q in q.