ISDN PRI hangs periodically,have to shut/noshut controller

[tonywen]

An ISDN PRI periodically hangs, 2 or 3

times a week. The fix is to shutdown the controller and no shut.

IOS 12.3(14)T7,2651XM.

ISDN q921 debugs turned on when problem

occurs. It shows that after this debug

Aug 15 05:34:44.075:ISDN Se0/0:15 Q921: User TX -> REJ sapi=0 tei=0 nr=68\

par the router never sends another User TX -> RRp and only sends TX -> RRf

Any suggestions on how to stop it happening?

[thomas.chen]

IOS gateway does not detect the correct ns value for a retransmitted q921 info message. this causes the t200 timer to increment which eventually will cause the E1 to reset.

[tonywen]

Hi Thomas

Thank you so much for the explanation.Much appreciated.

The problem is fixed by the telco.They had layer 2 issue.

Have a nice weekend.

Tony