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Cisco Bug: CSCub01423 - IOS does not send TCS/MSD/ACKs/UII without any debug enabled

Last Modified

Dec 17, 2015

Products (1)

  • Cisco 3900 Series Integrated Services Routers

Known Affected Releases

15.1(4)M4.1

Description (partial)

Symptom:
When calling from Nortel PBX via CUBE to IVR (H.323 provider) DTMFs are not recognized by IVR.
But after enabling any of debugs (like 'debug voice ccapi in out' or 'debug h245 asn1') DTMFs are recognized.
Looks like a timing issue.

Call flow:
Nortel > H.323 > CUBE > H.323 > H.323 provider > IVR

CUBE: 3925 IOS 15.1(4)M2 / 15.1(4)M4

We cannot capture any logs for the not working call because enabling of any debug makes calls working.

Based on sniffer trace (internal IOS sniffer ran on CUBE) we can see that in the not-working scenario CUBE does not send TCS/MSD/ACKs/UII messages on the second call leg (call leg to H.323 SP).
The other difference - in the not working scenario CUBE as the first send TCS and MSD messages on the first call leg (to Nortel). In the working scenario mentioned messages are sent after receiving TCS and MSD from Nortel. I think the change of sequence of messages can be caused by debugs running on the router which introduce some delay.

Conditions:
Two H.323 call legs, one of them towards Nortel PBX
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