Intermittent call drops on incoming calls on AT&T IPflex Fiber

Hello everyone,

This is kind of hail mary but I figured I’d give it a shot. I’ve got a pbx phone system running FreePBX version sitting on asterisk 11.10 on a CentOS 6.5 install. We are receiving SIP service from AT&T via IPFlex fiber. It’s sitting behind a pfSense firewall. The call quality is great and the system mostly works. However I’m getting intermittent drops on incoming calls and I can not for the life of me figure out what is causing it.

I’ve done Sip debugging until I was blue in the face and I’m no closer to figuring it out. I am getting some abnormal entries in the SIP debug. Such as:

SIP/2.0 405 Method Not Allowed Via: SIP/2.0/UDP;received=;branch=z9hG4bK00c1cafc;rport=5060 From: "Unknown" ;tag=as1e77f728 To: ;tag=aprqngfrt-upd7ev10000c6 Call-ID: [email protected]:5060 CSeq: 102 OPTIONS Reason: Q.850;cause=55;text="Call Terminated" Allow: INVITE,ACK,BYE,CANCEL,PRACK,INFO,REFER,UPDATE,MESSAGE,PUBLISH

It’s some problem attempting to communicate with what AT&T calls border elements. Unfortunately finding someone at AT&T that knows what they’re talking about any better than I do (which isn’t a lot) is next to impossible.

I’m more than willing to provide whatever logs/settings you need. Any help at all would be greatly appreciated.