[cisco-voip] ISDN PRI issue - busy calls

[Erick Bergquist]

Anyone seen this before? Out of the blue, inbound calls are busy. MGCP Controlled gateway with 12.3(11)T2 IOS. 3745.  I am aware of other issues in this release and am updating, but I've not seen the behavior below before.

Debug isdn q931 was a constant flood of just SETUP requests received. Thats the only q931 message, only the SETUP. Nothing else. 

ISDN was multi-frame established, mgcp was registered, MGCP keepalives occurring. I turned on MGCP debugs also and saw only keepalives and no MGCP Call setup requests, etc during constant q931 SETUPs. I'm going on all the B's were in use since we had constant stream of SETUP messages on different channels that caused busy. The router show voice port, show voice call summary commands showed no activity on the voice ports either during the problem time. 

Nothing in router log for 1-2 months , as it is just  a voice gateway and things have been stable. PRI is error free, no errors. 

I shutdown the D-channel on the router and brought it back up and that cleared the issue. I know this resets MGCP and re-registers but maybe D-channel reestablishing cleared something on telco side.