IRB - When on, does a router really become a switch?

[marcbutler]

Hi

Have been reading through some of the interesting discussions surrounding IRB posted. But it does not address one thing.

If the router is able to bridge traffic between two ethernet interfaces and each of those interfaces are connected to a switch, will the router, because it is essentially be acting as a switch, send out BPDUs to inform the switch of it's capabilities etc?

The reason I ask is that I have a client who wants to build in some redundancy, but without purchasing extra hardware (same old story!!). Hence, he wants to have two switches that are interconnected, all clients connecting to each switch (not dual-homed) and he wants his one 2611 to connect to each switch by it's two ethernet ports.

What I was thinking was that if the router is sending BPDUs, that could imply that it could participate in the Spanning Tree process, thereby detecting the loop that there would be in this system and shutting down one of the links.

Is that the case?? Any feedback on this would be greatly appreciated.

Rgds

Marc

[b-watkins]

Your thinking is correct. When you configure a bridge group (something like "bridge 1 protocol ieee") you are configuring the spanning tree protocol at that time as well. I have implemented just what you mention with the bridge group added to the ethernet ports and using a BVI for routing. The failover is not extremely quick (in my testing about 8 seconds), but it works.

[marcbutler]

Many thanks for your reply. Glad to know I was not competely off the chart!!

If this is the only failover option available within this network, would you say it is reliable enough for non-critical protocol traffic?