Grandstream Phones dropping registration randomly 3CX 16.0.5.619 AWS

[albertohitech]

We have Grandstream 2160's and 40s behind different firewall appliances with SIP ALG disabled on the recommended 1.0.11.6 firmware. The 3CX is hosted on AWS cloud. We have custom SIP ports for every extension. The phones drop registration if you login to the phone GUI it shows registered but on the 3CX it doesn't. We're not using custom templates and have the latest Grandstream templates installed. Rebooting the phones brings the registration back up. Anyone else having this problem?

 

[eddv123]

Welcome to why not to use multiple handsets and remote STUN. 3CX now only recommend 1-2 handsets on a single site due to the amount of issues that can be related to this.

With that being said we have some sites also with this amount of phones working fine - it is very hit and miss in the way that it works. My initial advise is to put in an SBC. If you cant do that for whatever reason try the following:

* Run a PCAP trace from 3CX and from the phone onsite capturing the registration process - this will give a good indication of what is going on here - you may possibly even see an ICMP "destination/port unreachable as an indicator: https://ask.wireshark.org/question/...achable-port-unreachable-to-original-message/

* Although done already your Firewall is the main perpetrator of issues with STUN (attached is a diagram I wrote for correct configuration with a Draytek on premise side).

* Although you say SIP ALG is disabled you find some firewalls require it to be entered via command line or support other features such as SIP Tranformations, SIP Helper etc which can also cause issues.

* Try changing your SIP transport on the phones to TCP (default is UDP) although not supported by 3CX yet I have found positive results doing this since TCP is a connection oriented protocol (SYN/SYN-ACK/ACK) and can keep firewall pin holes open.

Best of luck!