ISDN layer down for less than one seconds

[karthikeyanm]

*Sep  7 07:34:39.375: %ISDN-6-LAYER2DOWN: Layer 2 for Interface Se0/0/0:15, TEI 0 changed to down

*Sep  7 07:34:43.395: %ISDN-6-LAYER2UP: Layer 2 for Interface Se0/0/0:15, TEI 0 changed to up

I can see the above messages in my Voice gateway 2901. Its a new install.

As you can see the downtime is less than a minute. What may be the possible cause.

What may be the possible cause.

[Gordon Ross]

If it's a one off, I wouldn't worry about it. If it's occuring frequently, then you need to investigate.

The two main causes I see for this are:

- Mismatched clocking configuration

- Fault at the far end.

GTG

[karthikeyanm]

I see it frequently. The problem is I am not able to narrow when particularly this occours. It occours very randomly.

I have synchd with far end clock. I have tried to toggle CRC settings too.

[Gordon Ross]

If you are 100% certain your interface/controller configuration is correct ,*ESPECIALLY* clocking (i.e. who's clocking from who), then you need to look at the possibility of hardware problems either at your end, the far end, or even the line itself.

If the far end is a public telephone exchange, blame them - it's usually them.

One other thing you could try, is running a debug isdn q921, and logging to a syslog server. That might reveal something. (a debug isdn q931 might be useful too, just in case it's a particular call/channel causing the problem)

GTG