Backup for mpls interface

sounds like you are losing the logical pipe but the physical line stays up.

the traditional fix is to use a routing protocol (the assumption here is that the PE breaks the control plane as well as the data plane). Once the PE withdraws the route (or the route times out), your CE router uses dial up to find an alternate path.

there are some specialised routing "hooks" in a cisco router - look for enhanced object tracking or SAA on the cisco web site. this allows you to use ping or various other periodic tests from the router to change the routing table - which can then trigger the backup.

If your CE router learns any routes dynamically from the PE router, then you maybe able to use the Dilaer Watch feature to trigger the ISDN backup on the loss of one of those dynamci routes

for more info on the Dialer Watch feature see