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3.2 MGCP SRST Fallback dropped calls

CCM 4.0(2a)SR1a w/ 7960s on 7.1(1) - deferred, I know - w/ a 3845 on 12.3(11)T for SRST failback.

Testing the fallback feature had established external calls dropped, and the IP phone was then thrown into a state that disallowed any calls - internal and external resulted in reorder.

Tested in my lab w/ a 2811 on 12.3(11)T2, and 7960s on 7.2(2) and 7.2(3) behaved the same as the production network - internal calls persisted, but external calls dropped and odd behavior from the IP phone with an external call when the switch to SRST occurred.

What is the expected behavior w/ an MGCP controlled 3845 configured for 3.2 SRST?

Once the switch is made, all features function.


Re: 3.2 MGCP SRST Fallback dropped calls

I think I'm seeing the same behavior with a 3825. I'll share my details in hopes that it will save some troubleshooting effort.


IPPhones function properly, that is, they register and can call each other in SRST mode. Problem is, the gateway doesn't revert to h323 mode. PSTN circuit goes admin down and won't come back up unless I manually shut/no shut the controller.

Further, when ccm-manager once again can see the CCM and re-registers, the PSTN interface will not revert to MGCP mode without a manual shut/no shut on the controller.

ccm-manager fallback and call application alternate Default are configured. Indeed, the same config works just fine on an older 2651xm runing 12.2 code.

I've hunted the bug tool kit and release notes and not found anything that resembles this issue.

Hopefully someone will have some insight.


New Member

Re: 3.2 MGCP SRST Fallback dropped calls


There appears to be a history of this question - E1/T1 PRIs lose established calls through an MGCP controlled gateway.

There is a doc on CCO, but I haven't tested it out yet...perhaps it may be of some use.

Let me know if this helps.


Re: 3.2 MGCP SRST Fallback dropped calls

Hey Beau,

Thanks for the link. I ran across that link last night while troubleshooting. But I'm not sure I was being clear.

The fallback process, as described in the link, using the configuration pointers in the link, is not happening with my 3825. But using the same configuration, it does work as described with my older code and platform.

Where I'm at now I'm not sure if there is a newer configuration requirement in 12,3 or 12.4 that is not mentioned in that doc, or perhaps MGCP/SRST are just not supported in ISR, or we've got a bug.

Your post peaked my interest since it is ISR & MGCP/SRST related. However, if this is not what you're experiencing, let me know and to keep things moving for you, I'll withdraw and start another thread.

Thanks again,


Re: 3.2 MGCP SRST Fallback dropped calls

Just an update to my issue, not sure if it helps with the original post, but I suppose it could be related.

In any case, it could help you avoid some pain

In my ISR, I was using an older NM-HDV/VWIC-2T1-MFT combo with the older PVDMs that go in that NM. Calls in 711ulaw or 729, transcoding, conferencing all worked well. But call application alternate DEFAULT would not kick in.

I had to manually shut/no shut the T1 controller to force it to come back up in either fallback or mgcp mode.

Well, long story short, I just received the PVDM2 I'd ordered with the box. I removed the NM-HDV & PVDMs, placed the VWIC in slot 0/3/1, installed the PVDM2 in Slot 0, updated the configs with the new port info, and bounced the box.

Voila! MGCP w/SRST works great!! Can't explain why. I put the NM/PVDM with the same VWIC in a 2651XM, and it works fine. Go figure....

If anyone's seen a field notice or bug, please post it. I haven't yet found it.