[c-nsp] P to P T1 timing issue?

[Pete Templin]

Kienzle, John wrote:

> We are configuring our routers for a point to point T1 circuit.  We are
> using a similar config as we have had in the past with T1's. The problem
> we seem to be having is the connection goes up and down continuously. In
> fact, it will be up for 20 seconds, down for 10 seconds, and then
> repeats. It seems like some kind of timing issue, and after verifying no
> clocking from the Telco, we configured clocking on one router. That did
> not fix it. I believe our lead tech opened a TAC case for assistance,
> just wanted to get your thoughts too, before we schedule downtime to
> change out and try a different controller card.

Periodic flapping smells very much like a timeslots mismatch, depending 
on your L2 protocol.  Verify your CSU settings, whether Cisco internal 
('service-module timeslots 1-24', 'controller tX X/Y/Z; t1 Z chan A 
timeslots B-C', etc.) or external (years ago, we had a batch of Kentrox 
CSU/DSUs with faulty firmware: setting a management IP address on the 
unit would cause it to report timeslots in service that actually 
weren't.  Kentrox's web bulletin on the issue pointed directly to 
periodic flapping as the telltale sign).

pt