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SIP ALG Firewall checker failing behind my Watchguard

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Fred2k

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I have a Watchguard T10 (Fireware 12.0) sitting in front of my 3CX server. Last week whilst configuring the firewall I managed to pass all the 3CX Firewall Checker tests. At the time, I managed to resolve the SIP ALG test by adding an outbound rule from the 3CX server to any external on port 5060 (TCP & UDP).

Today however, when I run the firewall checker it's failing on SIP ALG, but nothing has changed on the Watchguard firewall! As far as I know there is no global setting within Watchguard to turn SIP ALG on & off. My understanding is that if you want SIP ALG, then you add a SIP ALG Proxy rule (which I haven't got).

Can anyone help?

Windows Firewall is completely disabled on the 3CX server btw.
 
Hi Cobalit. Yeah I followed that procedure (which was useful, although it's actually missing a couple of points, like you need to have outbound STUN and SIP ports open).

I've had confirmation from Watchguard that SIP ALG is only used on their device if you add a SIP ALG proxy, which I haven't.

I've made sure SIP ALG is disabled on the router too, so this is a real mystery.

I'm going to contact my ISP in case it's something at their end.
 
Hello @Fred2k

You can use wireshark to troubleshoot firewall checker issues. Run wireshark on the PBX machine in parallel with running the firewall checker. The use the following guide to see which ports are failing and why. https://www.3cx.com/docs/firewall-checker/
 
Hey @Fred2k

When you run the firewall diagnostics from 3CX what do you see in 'Traffic Monitor' from the Firebox System Manager?

That should hopefully give some clues as to why its blocking the port / traffic.
 
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