Block unwanted traffic on port 1720

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Block unwanted traffic on port 1720

L0 Member



I have a voice/visioconference system available on the internet (via NAT-ed IP) using H323. So of course the port 1720 is open and reachable from outside, without restriction on IP addresses because users must be able to reach the system from their smartphone App.

My problem is that sometimes, some traffic on port 1720 (shown as H.225 in the logs) is making the system ringing because a few packets go through the firewall even if it's not legitimate call signaling.

Because the incoming traffic is matching a policy on the firewall my Zone Protection Profile does not block.

How can I better protect this port? Any suggestions?


Thank you for helping,




L7 Applicator

Check logs if those "bad" calls come from same country where "good" calls.

Maybe you can block based on source country.

You use application based rules right (not port based)?

Enterprise Architect @ Cloud Carib



Yes I'm using Application-based Rules, and it is recognized as valid h.225 application.

I already limited the source IPs to some Countries, but I still have the same issue.

Because of the mobile Users I can't be to restrictive on souce IP addresses.

I think I will force the mobile users to use SSL VPN to access the Visioconf System and for the other office I can restrict the Access to a few well-known public IP.




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