Is it possible to backup a T-1 leased line with another T-1 leased line in a bridged environment?

[admin_2]

We have a pair of Cisco 2500 routers bridging another location. We want to replace the ISDN backup with a T1 connection. I have been told that it is not possible to perform a backup of a T1 line with another T1 line in a bridged environment. Can you clarify this?

[#2]

There should be no problem with doing this. You can configure a second bridged T1 the same way you configured the first. However, normal spanning tree rules will result in the second T1 being put in a blocking state, effectively shut down while the first T1 is up and running. You might consider configuring the T1s to run multilink PPP and run bridging over that, so that you get the full 3Mbps of throughput when you have both T1 lines available when both circuits are up. A failed line will be removed from the multilink bundle automatically. Here's a URL that will show you how to do it:

http://www.cisco.com/univercd/cc/td/doc/product/ong/15304/15304sfw/dcppp.htm

I would unconditionally recommend multilink, but a 2500-series router doesn't have much in the way of CPU and your traffic load might overwhelm it. It's up to you, you might try it and see how it works.