[cisco-voip] MGCP Odd issue

[Dave Goodwin]

Barry, if you have the q931 debug from when the error occurred, and if you
are able to share it, that may help shed light on the error. The mandatory
IE missing issue is an ISDN protocol error where the CUCM and telco switch
are in disagreement about something. It is sometimes possible to determine
which IE is missing from the debug of the entire failed call.

TAC may be able to provide help as well, if you can provide that debug for
them.

On Tue, May 26, 2015 at 3:53 PM, Barry Howser <bhowser5050 at gmail.com> wrote:

> Hi Wes. The "mandatory missing IE" message was at the end of a q931 debug
> right before the call goes busy. I may have over simplified my original
> explanation. I have several gateways that this exact same scenario happened
> to. All experienced the same condition, with the same configurations.
>
> On Tue, May 26, 2015 at 3:33 PM, Wes Sisk (wsisk) <wsisk at cisco.com> wrote:
>
>> a couple things here -
>>
>> you say MGCP.. if using MGCP and d-channel bachaul then it is CCM’s ISDN
>> stack in use. Where did you see the error “mandatory IE missing?” if it was
>> with debugs on the gateway then it may have been generated by the gateway’s
>> ISDN stack.
>>
>> each isdn ‘switch type’ has subtle nuances in implementation. the right
>> answer really depends on what physical equipment the telco is using as well
>> as how they have the d-ch provisioned on their end.
>>
>> it could be the telco changed config. or they might have upgraded the
>> switch. or you may have started using a different call flow that
>> added/removed IE’s.
>>
>> also possible that a lingering reset/restart was not applied on the UCM
>> side (CSCtw80866    Reset Required flag in CCMAdmin for any device/trunk
>> that has been )
>>
>> -w
>>
>> On May 26, 2015, at 2:44 PM, Barry Howser <bhowser5050 at gmail.com> wrote:
>>
>> So I've had an MGCP/T1 gateway up and running with CCM, happy as a clam
>> for several weeks.
>>
>> Then all of the sudden today it stopped passing inbound communication.
>> Egress works just fine, but ingress rings once then a fast busy.
>>
>> In the ISDN logs I get "mandatory information element missing".
>>
>> I am using; EF, BZ8S, Primary-ni (which is telco settings). Again
>> everything WAS fine. After some research I found that error to mean that
>> the CCM side kicked the call back to the gateway because it didn't get
>> everything it needed in the header.
>>
>> A proposed suggestion was to use a different switch-type. So in the
>> CCM/Gateway/PRI config page, I changed the switch type to PRI-4ESS ->
>> Saved/Applied/Reset (then restarted mgcp on the gateway) and presto,
>> ingress is now working.
>>
>> If I reverse the process and go back to the Primary-ni in the
>> CCM/Gateway/PRI config, I get the same problem with ingress again.
>>
>> Can anyone explain this to me? Does it sound like my telco changed
>> something? Seems like something with MGCP is goofed right? Is this
>> something that a telco would just arbitrarily change?
>>
>> Thanks
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>>
>
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