I recently came across a bug with Elastix 2.x in which outbound calls over a SIP trunk or PRI (E1/T1) drop after 30 seconds. From testing, this can occur with Counterpath X-Lite as well as Linksys PAP2 devices. The issue occurs at random and only affects some outbound calls. There is nothing noted in the Asterisk log, CDR log or system logs which makes the issue difficult to diagnose.
To resolve this problem you need to make two modifications, one to Asterisk and one to X-Lite:
1. Login to your Asterisk server.
2. Edit: /etc/asterisk/chan_dahdi.conf
3. Make sure the following statements are commented out:
4. Restart your amportal or reload Asterisk.
1. Open X-Lite
2. Select: Softphone > Account Settings
3. Uncheck: Send SIP keep-alives
4. Restart X-Lite.
These fixes should resolve the call drop issue.