T46G - No Audio on External Calls

[tgardner]

Hello!

We have a customer using 3CX 12.5 SP2 with a fleet of Yealink T46G model SIP phones.

The device in question is firmware 28.71.0.224, and currently lives at a remote site. It communicates with the PBX across a VPN maintained between two hardware firewalls. The IP address of the phone differs in the subnet from the PBX, but ping tests, etc., work fine.

The device is having the exact same issues as mentioned in this thread from 2013: http://forum.yealink.com/forum/showthread.php?tid=799

Updating firmware is not an option, as this firmware version was the only one that fixed an issue with calls being answered on random handsets on speaker, without warning.

To reiterate the basics:

- Internal calls to other extensions route fine, with audio just fine.
- External calls to the main office have audio just fine, but external audio is NOT routed to the target phone.

Anyone?