3CX Sip trunk to Skype doesn't try co connect

[Ab Abych]

Hello.

New trunk from 3CX to Skype servers was created by me:

But it have strange behavior - it have no date/time in "Register Sent" and "Register OK" fields, firewall and tcpdump shows no activity from 3CX PBX station to skype servers.
What should i do in order for 3CX tries to connect to skype servers?

 

[JohnS_3CX]

Hi

You set the trunk to IP based?

 

[Ab Abych]

You set the trunk to IP based?

yes

 

[JohnS_3CX]

Then there is no registration taking place with this option selected. You might want to delete the trunk and recreate it from the template. It can be found here under Worldwide providers:

 

[Ab Abych]

Then there is no registration taking place with this option selected.

Is it mean that authentication (in case of Skype) available only by Authentication ID and Authentication Password, no IP based auth?

 

[JohnS_3CX]

If I understood you correctly, then yes.

 

[Ab Abych]

Issue with no activity from 3CX PBX station to skype servers solved, but SIP trunk to skype servers still doesn't want to work.
Now 3CX PBX accurately send "REGISTER" request to skype server, and server respond "401 unauthorized". As described there, this is normal and 3CX must send "REGISTER" request with authorization credentials in "Proxy-Authorization" section after "401 unauthorized" answer received from Skype.
But (as i see in WireShark) my 3CX PBX still continue to send initial "REGISTER" requests without authorization credentials. Looks like answer from skype server silently ignored.Why?

 

[JohnS_3CX]

You can PM me if you like and send me a link to download the capture showing this behavior.

Make sure this capture was taken from the 3CX machine, not from the firewall or other networking device.

 

[Ab Abych]

link was sent

 

[JohnS_3CX]

Hi Ab,

Even though the replies from skype come back to the PBX interface, it's quite possible that the OS or something else blocks it.

This is derived from the fact that the PBX keeps sending invites while exponentially backing off (it delays more and more between invites if you look at the timestamps) and it's a good indication that the SIP service is not seeing those 401 replies coming back from skype tries to avoid spamming the registrar.

Can you please share some details about your setup before we proceed?

• 3CX Version, e.g. Standard Annual 16.0.2.910
• Server OS, e.g. Debian 9 / Windows Server 2012 R2 / Raspberry Pi
• Is the 3CX Server Hosted and where?
• Provisioning Method: Local / VPN / STUN / SBC
• Has the Firewall Checker passed: YES / NO

 

[Ab Abych]

3CX Version - Professional Annual 16.0.4.493
Server OS- Debian 9
Is the 3CX Server Hosted and where? - hosted locally on VMWare ESX virtualization
Provisioning Method - Local (not sure)
Has the Firewall Checker passed - NO, because 3CX SIP Server not available

 

[JohnS_3CX]

Ok first thing we need to do is get the firewall checker to pass. Provided you have not created any custom ports during installation, you can look at the standard ports here https://www.3cx.com/docs/ports/

If the ports are opened successfully on your firewall towards the private IP of your PBX, then all the tests should pass when you run the firewall checker here:

 

[Ab Abych]

@JohnS_3CX , we have a problem with SIP ALG check. Details in PM.

 

[JohnS_3CX]

Hi Ab,

You can run a capture from here to check your ALG
https://www.3cx.com/docs/capture-network-traffic/