I've been using FreePBX now with no real issues for >1 year with a Cisco 9971. The only changes have been updates to keeping the system patched. Yesterday I had to reboot the system for the first time in months and while incoming calls still work, outgoing now fails with the following error:
[2017-07-16 08:26:49] WARNING[C-0000000a]: chan_sip.c:25808 handle_request_invite: Received SIP INVITE with unsupported required extension: required: unsupported:sdp-anat
I did find this topic https://community.freepbx.org/t/invite-with-unsupported-required-extension/20614 however I don't see any Allow fields in the extension (at least in the web UI) to modify. I'm hoping I am missing something obvious but I figured it would be good to make a post as others are much better than I am at this and may be able to direct me faster.
At the moment the server is fully up to date and indicating it is FreePBX 126.96.36.199.