Cisco Call Manager Call Forwarding No Audio Issues

[rgranada70]

We are a company of @ 300 employees and we are on version 12.0.1.21900 of Cisco unified CM. The problem we are facing seems to be random. When our users set call forwarding on their Cisco IP phones, usually 7940 and 7960 models there are times when the call connects but the person answering the phone cannot hear the caller and vice versa. It does not happen all the time but we would notice maybe once every 4 calls or so. We tested amongst ourselves and the same thing happened. We have tried testing by calling our deskphones via our cell phones and would forward but only at random times does the audio drop. I suspect that this cannot be a setting of sort like calling search space because it does work most of the time but I am still scratching my head as to what could be the cause. Any ideas? 

[Ratheesh Kumar]

Hi there

Can you share more details here. Talking about CFA, is this issue appearing while forwarding to PSTN phones or internal numbers.

1. If its external, whats the CUCM - GW model. Is it SIP/H323/MGCP ?
2. Can you check the codec of those active calls ?
3. Any MTP in place for the calls 

If this is a SIP trunk , can you try enabling the MTP required check box and test the calls

Hope this helps!

Cheers
Rath!

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[rgranada70]

Hi,

The calls that had audio issues were stemming externally over SIP protocol. No MTP in place or at least not yet and the calls are in G711u encoded. Not sure can this be a firewall porting issue since it happens randomly?

[Ratheesh Kumar]

Hi there

Wireshark pCaps from the phone ports should be a best bet. What are the debugs says ?

Can you enable the MTP on SIP trunk and test it ? Is this affecting only on 7940/7960 models. Worth try upgrading the firmware on a couple of sets 

Hope this helps!

Cheers
Rath!

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