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New Member

Q931Backhaul issue, using MGCP with NM-HDV-E1

Hi all,

I'm facing an issue with a C3620, connected with MGCP to a CCM 3.2(2c).

H323 works fine, and calls go both ways to and from the CCM and the PRI.

If I configure the controller and the serial interface to handle MGCP Backhaul, my PRI get immediately disconnected, just after entering the "isdn bind-l3 ccm-manager" command.

Show isdn status shows:

ISDN Serial1/0:15 interface

dsl 0, interface ISDN Switchtype = primary-net5

L2 Protocol = Q.921 L3 Protocol(s) = CCM-MANAGER

Layer 1 Status:


Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = TEI_ASSIGNED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 0 CCBs = 0

The Free Channel Mask: 0xFFFF7FFF

Number of L2 Discards = 0, L2 Session ID = 6

Total Allocated ISDN CCBs = 0

And debug isdn q921 shows:

ISDN Se1/0:15 Q921: User RX <- SABMEp sapi=0 tei=0

ISDN Se1/0:15 Q921: User RX <- SABMEp sapi=0 tei=0

ISDN Se1/0:15 Q921: User RX <- SABMEp sapi=0 tei=0

It is running 12.2(11)T

1. Got an idea why backhaul is causing this, have I forgot something on the router, on the CCM ?

2. Is Backhaul mandatory for MGCP to work with CallManager, or can I keep my legacy ISDN settings on the router ?

3. maybe I'll have to keep H.323 settings for this customer......;-)

Thanks for your answer.



Cisco Employee

Re: Q931Backhaul issue, using MGCP with NM-HDV-E1

It's possible you have forgotten one or more settings on the router in order to properly configure PRI backhaul using MGCP. You can either stick with H.323 or if you have not looked at the documentation for doing MGCP with PRI backhaul please check here:

New Member

Re: Q931Backhaul issue, using MGCP with NM-HDV-E1

Thanks for your replies,

It's working now.

It appears to the PBX (Ericcson MD110), which did not deliver the rinback tone neither on a PRI or a BRI by default.

We changed these settings on the PBX, and now I get the ringback on the IP-Phone.

The Ericsson guy told me that its PBX was able to generate this ringback tone for incoming calls (ie if the router does not sends it).

Does the CISCO gateway can do this ? in my case, it would have been usefull !

Thanks, cheers,


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