Phone re-REGISTER on a 2nd connection although already registered

[Zivk]

Hi,

We have a certain phone (Yealink) that normally re-REGISTER to FusionPBX 4.4.3 + FreeSWITCH 1.8.4 in a fixed interval, but sporadically attempts to re-REGISTER sooner, apparently on a different TCP connection.
FreeSWITCH agrees and puts two "contact:" headers in the "200 OK" response, e.g:

Contact: <sip:3001@51.29.152.18:5060;transport=TCP;received=51.29.152.18:12089>;expires=140
Contact: <sip:3001@51.29.152.18:5060;transport=TCP;received=51.29.152.18:12091>;expires=600

This phone behaves correctly (both on UDP and TCP) when connected to two older FusionPBX + FreeSWITCH systems (not sure the version is important).
The phone returns to normal after a while (5-20 minutes) when it makes another re-REGISTER, successfully.
The phone is connected through NAT, and so is FreeSWITCH.

How can this happen? What could make the phone think that registration to this specific system is lost and make a new one?

Thanks.

 

[DigitalDaz]

Your NAT tunnels on the router are timing out, bring the registration time to 120

 

[Zivk]

Thanks @DigitalDaz.

 

[DigitalDaz]

You solved?

 

[Zivk]

The problem is sporadic and hasn't happened in the last week or two on any phone, those with 300/600 sec REGISTER interval and those with 120 sec. We think it's related to some changes at the SIP provider. We're following it up.

 

[DigitalDaz]

What haveyour sip phones got to do with your provider, its NAT, plain and simple. It will vary by router and the protocol. You will probably also see better results with TCP.