3cx working fine but firewall test failed then opened udp 3478-3479 and now passed

[Shawn]

my firewall test was failing but everything is working fine. i looked into the firewall checker guide and noticed they ran a packet capture for udp 3378-3379. i duplicated the test and noticed that i was not getting a binding response. i have a sonicwall so i added udp 3378-3379 to my services and added it to my 3cx services group. this updated my outbound rule to allow these ports. now i get the binding response and my firewall test is passing.

i have a dedicated internal network for our phone system. my outboun rule states, for traffic from voip to wan with any source and any destination using 3cx services (which includes all 3cx required ports including 3378) to be allowed. i have another rule after this one that denies everything else.

i'm no network expert and would appreciate if someone could explain what's happening here. the sonicwall setup procedure at 3cx does not say anything about port 3378-3379.

basically my firewall test fails when i don't allow 3378 and passes when i do allow it. is this only for the 3cx test stun server?

thanks

shawn

 

[Saqqara]

Sounds to me if 'Disable Source Port Remap' is not ticked , ports 3378-3379 are not used by 3CX

https://www.3cx.com/docs/sonicwall-firewall-configuration/

 

[StefanW]

3378-3379

do you mean 3478 and 3479?
They are not used by 3CX as PBX however STUN server work on those default ports.
So the request been send from your PBX, lets say from Port 5060 is send to 3478/3479 and is answered from those.

If you have locked down DST ports / IPs then they, the test will also fail as also the PBX will fail to determine the Public IP address in "Dynamic Mode"

 

[Shawn]

disable source port remap is checked on the outbound nat policy. that was the first place i went and it did not make any difference.

ports 3378-3379. attached is a screen shot from the 3cx firewall checker and here's a link to the article i'm referencing

https://www.3cx.com/docs/firewall-checker/