Calls Dropping after 30 Seconds

[vbreyter]

Outgoing calls originating from our deskphones (GXP 2170s) are dropping after 30 seconds. After come research I discovered that 3CX was not receiving ACKs from the deskphones and was thus terminating the call. Looking at captures from both 3CX and the deskphones it looks like the 200 msg from 3CX has the wrong IP address on the CONTACT header. The deskphones are actually sending ACKs, but they are sending them to this wrong IP address and therefore 3CX is not receiving them. I do not recognize the IP address that 3CX is using in the CONTACT header, whois says it's an AWS address, but it is not the private nor public address of our 3CX server.

Our networking setup is:

3CX hosted on AWS <---internet--> Firewall (Fortigate) <---LAN--> Deskphones

I also took one of the deskphones home and I have the exact same problem so it's not a problem with our firewall.

All the deskphones are provisions using the remote STUN option.

This is only a problem on outgoing calls originating on the deskphones. Everything is fine when using the 3CX app.

 

[Naveen | Cal4care]

Hi vbreyter,

Did you disable SIP ALG on your Fortigate firewall?
Please refer the manual https://www.3cx.com/docs/fortigate-firewall-configuration/#h.zafmfh1gwae8

As per 3CX recommendation, if you have multiple IP Phones connected in to the same location, then you must use 3CX SBC.

The 3CX Session Border Controller (SBC) is a software service that installs in your local network to allow easy connection of IP Phones to a 3CX instance in the cloud, hosted either in your private cloud or by 3CX. The 3CX SBC combines all SIP (signaling) and RTP (media) VoIP Packets from one location and delivers them to the cloud PBX, thereby overcoming common firewall and networking issues that affect reliability.

Note: 3CX App uses tunnel port 5090(UDP & TCP), but IP Phones uses port 5060 (UDP & TCP)
Please refer this guide for more details. https://www.3cx.com/docs/manual/firewall-router-configuration/

 

[leejor]

I do not recognize the IP address that 3CX is using in the CONTACT header, whois says it's an AWS address, but it is not the private nor public address of our 3CX server.

3CX does not just make up an IP address, so, it is getting this from somewhere. Have you looked over all of the settings, to be certain that it was not entered, in a field, in error?

 

[ChrisC_3CX]

I do agree with Naveen | Cal4Care regarding deploying a 3CX SBC on a remote site that hosts multiple IP phones. However, I am yet not sure whether or not this will help the situation you're currently facing.

Looking at captures from both 3CX and the deskphones it looks like the 200 msg from 3CX has the wrong IP address on the CONTACT header.

Have you checked the 200 OK message on both IP phone and 3CX PBX packet captures, do they both have the exact same IP in the contact header?

You said you don't recognize the IP, have you happened to check it against the one the FQDN resolves to just in case? Regardless of whether you recognize it, is it a public or a private IP?

As leejor mentioned, the PBX must be getting this info from somewhere, provided of course it is the one placing it there. Access the Management Console, go to Settings >> Network and make sure everything there is correct too.