Momentary one-way audio during transfers

[coconino1969]

Hello everyone

Working with

CUCM 9.1

CUBE

We have just moved to a new tel-co SIP trunk for our external calls, everything went pretty smooth but we a single location with the scenario below -

If  a user  calls in and asks to be transferred to anyone, there will be one way audio at the caller end, we can hear him but he cannot hear us.

I have been going around checking resources, codecs, region settings and phone configurations. The strange thing is that only happens at this location - 95% of the other phones work fine when transferring which leads me to believe that is not a system wide setting I'm looking for.

Any suggestions would be greatly appreciated -

Thanks 

Jose

[Deepak Mehta]

I had faced similar issue where transferred call was going via a another gateway and we didn't have routing in place for that .

So you might want to check what is egress for transffered call and does it have any firewall in between.In most of one way audio issue it is most likely either firewall  blocking the RTP packets.

What error message do you see in SIP logs?

[coconino1969]

Deepak - Thank you for your quick reply

I should have added that the one way audio only lasts about 10 seconds after being transferred , after that time it returns to normal. We presume its not system wide as only a single office with about 30 users is experiencing the problem. 

Gathering the logs tomorrow - Everyone has gone home for the day.