I recently upgraded to 188.8.131.52 and have been live in production for over a month. We had an issue this week with the sip trunk to our VoIP provider I rebooted the server. It didn’t fix the issue however i latter found the issue to be on my router and finally i had inbound calls again, however users then started complaining that there phones where not registering. I narrowed it down to phones that use PJSIP. We use mix of Cisco 7961 and 7841 having migrated from CUCM. I use a 7961 which uses chan_sip which is why i didn’t notice the issue. Pulled my hair out for an hour on this and as i was stretching the patience of my business i reverted to the pre upgrade VM which i had preserved and everything started working fine again.
Later that night i rolled forward again to the upgraded VM and the issue was still present. Cut a long story short i found that the SIP Channel Driver setting in advanced settings had reverted itself to Chan_sip only. After changing to both again everything worked just fine. I rebooted a few more times and could not replicate it happening again.
What would be the reason for this occurring? Is there any checks or balances done at reboot that would influence this setting? Anything I can do to ensure it doesn’t occur again?