30% of phones go offline and then reconnect

FreePBX Endpoints
1

I have an install with 2 systems and around 400 phones, all local to a pbx. The pbx has tremendous horsepower and shows no signs of being stressed. Once or twice a day 30-50% of the phones will failover to the secondary server and then 3-5 minutes later register back with the primary server. There is no rhyme or reason which phones will failover. Does FreePBX have a UDP session limit? The phones do have a failover SIP server and every 15s they send a SIP option packet to the primary server to see if it’s there. Perhaps this is causing issues?

2

There are no hard limits. You would need to look at the logs to see if any overload mitigation was in progress, although my first suspect would be the network.

3

Most likely it is a network and/or firewall problem that is closing the sessions. To mitigate this, I initially set many useful parameters on the phone (Grandstream) to keep the registering as

Register Expiration 5 minuts
Subscribe Expiration 60 minuts
Reregister before Expiration 240 seconds
Enable OPTIONS Keep Alive
OPTIONS Keep Alive Interval 30 seconds
OPTIONS Keep Alive Max Lost 3 packets
SIP Registration Failure Retry Wait Time 20

also reduced the custom sip headers due to the fragmentation of the udp performed by the firewall (Fortigate)

In the end I cut the bullet, as the firewall got in the way with “alg sip” systems, I switched to register extensions over TLS with TCP and SRTP and now I live happily

4

I looked through the logfiles and found no warning signs for another outage this morning. The phones are spread out amongst various buildings which are all connected on a single network so I wouldn’t think there are any NAT issues here. The odd thing is when a segment of phones go offline even phones on the same switch as the system will failover to the secondary server and then come back. It’s not like just a single building is dropping offline. It will also happen in the middle of the night so I wouldn’t think it’s a resource issue

5

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.