Solved Incoming calls from SIP Trunk Stops Intermittently

[kavijoshi]

Hi
I am facing the issue of Incoming calls from on-premise SIP Trunk stops coming after 5 min of last outgoing call and resumes again after 27 min of last outgoing call and again stops after 5 min (cycle continues...).
Configuration is 3cx on Windows 10 with 2 NICs - One for internet and extensions, second for SIP Trunk (On-Premise, no authentication, IP Based).

Wireshark capture on SIP Trunk Interface has revealed a pattern in the stoppage of incoming calls. There are packets of IGMP, ICMP and MDNS appearing every approx. 27 min, when this happens, incoming calls resume for next 5 mins, after which they again stop. Incoming starts and works for 5 min when either these packets appear or there is an outgoing call.
I dont have knowledge about these packets.

Picture attached.
Any advice how to resolve this?

 

[YiannisH_3CX]

Hi @kavijoshi

It looks a lot like a firewall issue where the session drops after 5 minutes of inactivity so inbound traffic is being blocked. The 27 minutes timer might be because the registration timer of the trunk is set to 30 minutes by the provider so the PBX will try to refresh it every 27 minutes. So the connection opens on the firewall and drops again after 5 minutes of inactivity.

I see 2 possible solutions for this:

1. Fix your firewall to allow for longer sessions.
2. Ask your provider to reduce the reregistration timeout to less that 5 minutes or enable OPTIONS (keep alive packets)

 

[kavijoshi]

@YiannisH_3CX
Thank you for the reply, I followed up on this with SIP Trunk provider. They have enabled OPTIONS at 10 sec interval. With this everything is working fine.

Issue is resolved.

Just one question, is 10 second interval too small? will it cause any issues with PBX as it will raise so many requests?

 

[YiannisH_3CX]

Thank you for the reply, I followed up on this with SIP Trunk provider. They have enabled OPTIONS at 10 sec interval. With this everything is working fine.

Issue is resolved.

Glad to see the issue has been resolved.

Just one question, is 10 second interval too small? will it cause any issues with PBX as it will raise so many requests?

That depends on the rest of your traffic. If its a busy system then i would recommend increasing it slightly. Maybe 30 seconds or a minute. But it there is not too match traffic for the specifications of the system then the 3CX PBX can handle it without any issue. OPTIONS messages in general require very little processing power.

 

[kavijoshi]

Noted. Thanks for the help.