You will want to use some method of DDR. Check out this site and you will find your answer:http://www.cisco.com/warp/public/123/backup-main.html

Try looking at FastEtherChannel, this might be the redundancy you are looking for:http://www.cisco.com/warp/public/473/4.html#2k6

When you do your debug isdn q931 and ppp neg, look for cause code:*May 25 22:44:36.340: BR0/0:1 LCP: I TERMREQ [Open] id 180 len 4*May 25 22:44:36.340: BR0/0:1 LCP: O TERMACK [Open] id 180 len 4*May 25 22:44:36.340: BR0/0:1 PPP: Phase is TERMINATING ...

Here is a sample config for the central (PRI router) set up with dialer profiles:controller E1 1/0 framing esf linecode b8zs pri-group timeslots 1-24interface Serial1/0:23 no ip address encapsulation ppp dialer pool-member 1 isdn switch-type primary-...