Symptoms

When clicking Apply Config in the GUI, or executing fwconsole r from the command line, IAX2 trunks that have a server specified by FQDN start to become UNREACHABLE.

The following errors are observed:

{{
[2016-04-05 14:58:16] ERROR[5759]: netsock2.c:524 ast_sockaddr_hash: Unknown address family '0'.
[2016-04-05 14:58:28] ERROR[6047]: netsock2.c:98 ast_sockaddr_stringify_fmt: getnameinfo(): ai_family not supported
[2016-04-05 14:58:38] NOTICE[5581]: chan_iax2.c:12311 __iax2_poke_noanswer: Peer 'voipms' is now UNREACHABLE! Time: 18
}}

A wireshark trace shows that after the POKE/PONG/ACK sequence changes to POKE/PONG only (i.e. the ACK is missing).

Background

This appears to be related to an old dnsmgr issue where the port is set to 0 if name resolution failes, but is never restored to 4569 when name resolution is restored:

https://issues.asterisk.org/jira/browse/ASTERISK-128301
https://issues.asterisk.org/jira/browse/ASTERISK-238131
https://issues.asterisk.org/jira/browse/ASTERISK-237671

Steps to reproduce:

I was able to reproduce this twice in a row using the following steps:

1. Install FreePBX 10.13.66 from ISO into a VM and install updates
2. Configure an IAX2 trunk that uses FQDN for the server name
3. run fwconsole r

Detailed troubleshooting steps were posted here: http://community.freepbx.org/t/apply-config-causes-iax2-trunk-to-become-unreachable-when-using-asterisk-13-solved/34224/1