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New Member

B-Channel OOS


The Call Manager Event logs if silled with the error mentioning the B-channel is down for MGCP gateway, the vendor confirmed that they are not able to find any alarms, I checked the port speed, that seems to be fine, should I run Q931 trace or how to determine the issue and resolve.

I am losing calls on all the channels on the gateway.

Thanks in advance.


Re: B-Channel OOS

Few things to check:

You can enable 'debug isdn q931' on the gateway.

As well, check 'show call history voice last 100 | i Cause' 10 is 16 which is normal, 13 is busy, and 19 should be no answer. Other causes are possibly dropped calls.

Particularly bad are cause code 47 (note the show command above is hex) 34, 38, and 127. Those are the most common for dropped calls.


New Member

Re: B-Channel OOS

Thanks for the response Nick,

This is for a CAT device, the Erroe messge on CM:

09/09/2009 07:15:25 Cisco CallManager Error None 3 N/A CALLMANAGER02 Error: BChannelOOS - B channel out of service.

Reason [Optional].: 0

App ID: Cisco CallManager

Explanation: Indicated B channel has gone out of service.

Recommended Action: Contact TAC for help if this alarm continue to generate.

The Dicktracy log: As attached

I appreciate your help on resolving this.


New Member

Re: B-Channel OOS


Just to share, the issue is resolved. The vendor had fixed the issue in their network, initially they said that their network had no such problem, however later informing them that we have check CPE and found no problem, then they accepted and resolved the issue.