Customer has a 7100 V4.82, 1 4DLM Card, 4 MGI License,Two Digital Phones, 16 3105 Phones, 3 of those are remote at another location 10 miles away. They also have (1) Polycom SIP Conference Phone at the remote location. Comcast is the provider at both sites.

The remote Polycom SIP Conference Phone Has Two Way Audio For Every Call To and From Main location no matter what type of phone calls it.

Digital Phone at main location calling remote VOIP phones OK.
Remote VOIP phones calling a digital phone at main location OK.

VOIP Phone at main location calling out to a remote VOIP phone has two way audio most of the time.

VOIP Phone at remote location calling a VOIP phone at the main location, no audio either way most of the time.

By the way, Clearfly SIP trunks work 100% of the time. No audio issues.

So it looks like everything is good on UDP 5060.

What is the issue?

Main site has a Netgear Nighthawk firewall and a Comcast Cisco DPC3939B router/firewall set in bridge mode.

Based on Samsung's recommendation, we have already replaced the MP10a and nothing really changed.

The last thing to do is to default, move up to V4.91 and reprogram by hand.

I still think it is a firewall issue of some kind.

What do you think?

MikeS in VA