"routing" over layer 2 connection

[DIEGO ALONSO]

My company would like to experiment with a L2 wireless technology from Motorola called Canopy. Canopy creates high-speed, layer 2, point-to-point links in a metro are using antennas with line-of-sight connections to our buildings. We currently have routers, subnets and serial circuits connecting these buildings. I don't want to convert my network to one huge subnet. I would like to keep my subnets and replace the current T1 lines with DSL lines for backup. I need a routing solution that would use the layer 2 links under normal circumstances to connect subnets but could switch to using the DSL and VPN if the Canopy network went down.

I am thinking using a L3 capable switch somehow but I am not sure how. Any suggestions?

Thanks,

Diego

[michelpe]

What you probably want to do is rely on some routing protocol like OSPFover the Wireless link, wich you can backup by using static routes pointo to the DSL or VPN router.

In that case the normal traffic flow should go over the wireless link. If that goes down also the routes will disappear and thus static routes will come into play

[DIEGO ALONSO]

Do you mean something like this: Canopy devices have an ethernet interface on the LAN side but no IP address therefore I don't know how the router would know that the Canopy is down. I was thinking of having a subnet that would be used for all router ethernet interfaces connected to the Canopy network. This way, the next hop IP for the router would be on the other side of the wireless cloud. If the router can't talk to the "remote" IP then the wireless must be down and the router would switch to a higher cost route that would point to the DSL. The question here is: What event makes the router drop a route? The next hop is not physically connected to the router, its just an IP address on a layer 2, ethernet like segment. Will the router ping or ARP for that next hop IP to determine its up/down state?

Thanks,

Diego