Grandstream phones go offline from FreePBX after registration timeout expires

Grandstream GXP2160 won’t re-register after Register Expiration time is exceeded. In troubleshooting this issue I have found the section under Asterisk SIP Settings - Chan SIP (A) - Registration Settings. What do I set the minexpiry, maxexpiry, and defaultexpiry too? Are these settings in seconds or minutes and could anyone explain these settings please? My pbx & phones are both on an internal LAN. My SIP trunk is to an external VOIP SIP trunk provider. Once they go offline I get an error of: “Unable to create channel of type ‘SIP’ (cause 20 - Subscriber absent)”. The phone still thinks it is registered but Asterisk says it is not. Any help would be appreciated.

I had to just do trial and error as I am not finding any information on these settings. What I found is in my Granstream phone I had to have the Register Expiration field set to a value that falls between the values set in FreePBX Registration times. I also made the Reregister before Expiration set to 0 in the phone.

For Example:
Phone Config - Register Expiration = 5 min
Phone Config - Reregister before Expiratoin = 0
FreePBX - Registration Times - minexpiry = 240 secs
FreePBX - Registration Times - maxexpiry = 360 secs
FreePBX - Registration Times - defaultexpiry = 300 secs

  • A big problem I ran into when trying to figure out how these changes affected registration timeout was that asterisk has a hard time letting go of the existing timing session. So when you change it and reboot the phone it may start an additional timer. Then it gets very confusing in the logs. I found the best solution was to make the changes to the phone and asterisk and then unplug the phone for the duration of your Register Expiration time. You will finally get a warning in the log that says Warning Retransmission timeout reached. Then its safe to plug it back in. When my phones were finally working correctly Registered SIP 'ext# at messages in the log actually stopped coming in at all and my phones stayed online and registered.

Hope this helps someone else as it was a huge headache for me.