MGCP PRI connected to PBX

Unanswered Question
Aug 13th, 2007


I have installed 2 2800 series with MGCP and Callmanager 5.1

The first one is connected to the PSTN (PRI)

The second is connected to a PBX (PRI)

the problem I have is when the second receive a call from the pstn, the isdn debug output is:

Aug 13 14:37:23.642: ISDN Se1/0/0:15 Q931: TX -> SETUP pd = 8 callref = 0x0002

Sending Complete

Bearer Capability i = 0x8090A3

Standard = CCITT

Transfer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0xA9838A

Exclusive, Channel 10

Calling Party Number i = 0x00A1, N/A

Plan:Unknown, Type:Unknown

Called Party Number i = 0x80, '5220'

Plan:Unknown, Type:Unknown

Aug 13 14:37:23.666: ISDN Se1/0/0:15 Q931: RX <- ALERTING pd = 8 callref = 0x8002

Channel ID i = 0xA9838A

Exclusive, Channel 10

Aug 13 14:37:31.734: ISDN Se1/0/0:15 Q931: TX -> DISCONNECT pd = 8 callref = 0x0002

Cause i = 0x82AF - Resource unavailable, unspecified

I have this problem too.
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csco11063007 Thu, 12/06/2007 - 10:45


did you solve this issue.if yes could you please share the solution.

i an facing the same problem

thanks in advance


yxsjwsb Fri, 12/14/2007 - 23:30

It may not help here, but I use a demo version of a PRI Debugger program out there. go to

I'm waiting for the full version to come out next month.

yxsjwsb Sat, 12/22/2007 - 10:00

The first beta of this PRI debugger had some issues, there's a revised beta posted at now.

yxsjwsb Thu, 01/03/2008 - 10:20

Just FYI - you can grab the full version of a debug isdn q931 log analyzer dirt cheap at It's alot easier than watching the logs scroll.

pcameron Thu, 01/03/2008 - 14:39

Q931 decoders are not going to help here. The debug traces clearly show an outgoing setup, the far end rings for 8 seconds and then the call is cleared from the gateway.

This means there is nothing wrong with the ISDN side of things.

Most common reason you see 'resource unavailable, unspecified' clear code is due to a codec mismatch on H323, or a lack of dsp resources on the router for either normal call processing or transcoding/conferencing/mtp. Since this is under MGCP control, the codecs are specified under the CCM control so there should be no mismatch.

Therefore we need to see what is happening at the MGCP side of things. Make a single test call and obtain the log from 'debug mgcp packet' , then turn this debug off and get a log from 'debug voip ccapi inout' for a similar test call. Make sure you do this when only one call is up (the debugs are too hard to follow otherwise)

Also attach a SH VER, SH RUN and SH DIAG output.

Mark Pareja Thu, 01/03/2008 - 23:18

Post & Cameron,

I experienced the same behavior once I exhausted all my DSP Resources on my 2800's that hosted my Pri Trunks at a previous company. The solution was to purchase more PVDM's and calculate my DSP requirements more accurately. I recommend using the Cisco DSP Calculator that can be found here.

Remember the more complex the Codec the more DSP resources you will end up using.


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