@danievr said in Current pfSense (through to at least 21.05.2), SIP phone behind firewall, incoming call audio cuts out after 25-30 minutes, how to fix?:
@tea Have you fixed it? Things you could try: NAT keepalive of 15 seconds; Register Expires 30 secs; If supported, use TCP instead of UDP; If your calls are proxied through your provider's servers, they might terminate the call based on policy. dslreports.com has a lot of info on VOIP.
It turns out that this most likely was something in the interaction between the particular VoIP phone and the particular IP telephony provider through which I received most of my incoming calls.
For reasons unrelated to this issue, I ended up needing to switch VoIP providers. Having made the minimum changes necessary to connect to the new provider (essentially server and authentication details), the problem seems to have disappeared.
I wish I knew what the actual problem was, but at least it's working for me now.