T1 Flapping

[irfan]

Remote Sites are connecting Corporate via Frame. Every now and then, T1 starts to bounce (carrier issues). This causes IP Phones to register to local gateway (SRST). As soon as the T1 comes back up, Phones re-register with central site (call manager); T1 goes down, Phones re-register with gateway...and so forth. There is no backup to this line. Phones are pretty much re-registering all the time.

We are using one default route statement at the remote sites, no dynamic protocols. Is there any way we can delay this routing after T1 comes back up so the phone traffic does not get routed to the corporate site? I don't want router to start routing as soon as the T1 comes back up and wait for, say, 10 minutes before it decides to use the line.

[jasyoung]

There's a new solution to this called IP Event Damping, available late in some 12.2 trains and mainline 12.3. It "penalizes" the T1 each time it goes up and down using an algorithm very similar to BGP route damping, and will wait for the line to stabilize before permitting routing to come up.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080110bc8.html