Solved 3CX not using default RTP port but using port allocated for QM

[vashil]

Hello all,
we are using 3CX version 15.5.
we are using default RTP Ports from 9000-9255.
however, when we take a PCAP, we find that the ports being sent for RTP is 13372 (for example), which is the allocated port for QM RTP Traffic.
Do you know what is causing this discrepancy?

thamls/.

 

[StefanW]

does your firewall checker pass without errors?

 

[vashil]

Failed, but ports are open on firewall.

 

[JohnS_3CX]

Hi vashil, does the the SIP ALG test fail?

 

[vashil]

Yes, but here the issue is with the rtp ports. How would sip alg cause rtp ports to be modified?
Thanks for your light

 

[JohnS_3CX]

It is recommended to disable your firewall's SIP ALG and also ensure that you have full cone NAT. Your firewall might be remapping the ports. I would recommend reading the below article to ensure your firewall check passes the tests: https://www.3cx.com/docs/troubleshooting-firewall-checker/


Note that the maximum port range 3CX uses since V15.5SP6 is:
External Port Range Change: 9000-10999 [UDP]
Internal Port Range Change: 7000-8499 [UDP]

 

[vashil]

Still not working. Is there any parameter that determines the destination port in the Invite Message that I send out?
or is this the normal working scenario?

 

[JohnS_3CX]

Has the firewall test passed all checks? Also if your PBX is 172.16.6.107 then it is using the correct port range, the provider however can ask your PBX to send traffic to a higher port, this would be normal behavior in this case. Keep in mind the PBX will only receive between 9000-10999 [UDP] but it will send to the provider in any port they request.

 

[vashil]

Closing this thread. It is indeed the peer end sending this information.

 

[JohnS_3CX]

Thanks for updating the thread