ISRG2 MGCP PRI Gateway - Inbound calls failing

[sjones@techsgi.com]

Having issues with a gateway that is setup as MGCP with 3 PRIs coming into it.  Recently, there have been reports with two of the DIDs (that the client is aware of currently) where the call drops.  In the Q.931 debugs, I see a mandatory information element missing message.  It sounds remarkably like bug ID CSCtf08864, but the version of IOS they're running should have the fix for it (all the elements in the bug match the environment, though).

PRIs are configured as primary-ni.  The only thing I saw that looked out of place was the service parameter for overlap receiving in CallManager is set to True by default.  I did see a couple cases where disabling that seemed to fix the issue, but I'm not sure what the potential ramifications would be if I did change it (downtime, etc.).

CallManager version is 9.1.2, gateway IOS is 15.2M(5)

Any ideas are greatly appreciated

SJ

[Manish Gogna]

Hi Scott,

Overlap signaling requires that called digits be sent one-by-one as they are received from the calling device. For Q.931, the first digit is sent in a call setup message and subsequent digits are sent in information messages. This technique is used when a receiving PBX must be able to recognize variable-length phone numbers, and requires that the sender signal the end of the call setup process. For Q.931, a “sending complete” message is used for this purpose.

Can you share the debugs of a working and non working call for comparison to see if this parameter indeed is causing the issue.

Some useful info about this parameter here

http://www.cisco.com/c/en/us/support/docs/voice-unified-communications/unified-communications-manager-callmanager/21977-overlap-send-rec.html

Manish

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[Mohammed al Baqari]

Hi Scott,

Please share the output of debug isdn q931 and debug mgcp packets.

You can create mgcp filter to match debugs for DIDs which are reporting the problem