[cisco-voip] MGCP PRI Issue

[Wes Sisk]

It's a stretch, but yes, sort of.

With MGCP backhaul the q.921 frames are terminated on the router and q.931 frames are received at the router and back hauled to CUCM.

For that to work the router must successfully download config from CUCM to get the configured ISDN protocol. Is TFTP download from CUCM to router working? Is that config applied successfully? "debug ccm-manager" or see the Multiservice debug lookup tool.

After that the serial interface has to come up an q.921 has to start coming up. At that point router will initiate a TCP session to CUCM and send a DL_Estab_req message. If that session fails to come up for any reason then registration will never really happen.

MGCP depends on much communication with CUCM. Generally it helps with problem isolation to try to terminate the PRI just on the router. Skip the MGCP config and use a basic h.323 setup. If the d-ch and PRI still do not come up then you have a signaling problem between the carrier and your router. Also, with this setup you can change the ISDN switch type directly on the router in global config or under the specific interface.

-wes

On Mar 7, 2013, at 6:40 PM, "Heim, Dennis" <Dennis.Heim at wwt.com> wrote:

I am running 15.1 IOS (3925) and Callmanager 8.6(1). We are integrated to a Nortel PBX, which is configured for PRI-NI2. When the gateway is configured for MGCP, the PRI largely does not come up. However, we see ISDN Q.931 messages referencing communication on channel 64. Obviously this is not quite right. Occasionally, the PRI will go into service and the message of channel 64 goes away. If we do a no mgcp/mgcp when it is working it usually does not come back up. If we switch to h.323/sip, the PRI comes up no problems.
 
Has anyone seen anything of this variety?
 
Dennis Heim | Sr. Unified Collaboration Team Lead
World Wide Technology | 314.212.1814 | dennis.heim at wwt.com
“Creating Impact, Ignition & Scalability”
 
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