MGCP and Cisco UCM issues when using different PRI timeslots?

Unanswered Question
Jun 14th, 2010

I have an issue in regards to MGCP and Cisco UCM7.

I changed our timeslots from 23 channels (1-24) to 15 channels (1-15,24).  And it works great!

Until the router reboots and Cisco UCM via MGCP overwrites the configuration back to 1-24.

So Cisco UCM is definitly overwritting what is on the voice gateway router.

What can I change in Cisco UCM to NOT do this or that we are using the first 15 channels of the PRI?

Thank you!

I have this problem too.
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ryabutler Mon, 06/14/2010 - 18:20

WOW.  Not supported.  That is not a good thing and don't understand why. 

So, if I remove those commands will we ....

1) Still be able to place and recieve calls through that gateway?

2) Still be able place and recieve calls throught that gateway if it is rebooted?

Question #2, is probably my biggest concern.

Thanks for the help!

Jonathan Schulenberg Mon, 06/14/2010 - 19:29

To be more specific, this is not supported with MGCP because UCM does not support fractional T1 circuits. This is entirely possible if you use H.323 or SIP on the gateway instead of MGCP.

Your ability to place or receive calls will depend on the channel selection order and call volume. Either way, when you hit a channel that is not in service the call will likely fail. UCM (which has no idea of the limited timeslots) is controling the Q.931 signaling which includes the timeslot selection.

Jaime Valencia Mon, 06/14/2010 - 19:55

The link I posted explains how to busy out the channels so you don't hit a nonworking channel. But it clearly explains this won't be supported

For a workaround, use H.323 instead of MGCP if a fractional PRI is necessary.

As an alternative, busy-out the B-Channels that you are not using in Cisco CallManager by performing these steps:

Note: This procedure is not TAC-supported.

If you want TAC support you'll have to switch to H323.



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