CheckPoint R80 H.323 Woes


As you may have read previously in my CheckPoint R77 to R80 article – There are some fun nuances and slight changes. I did the first policy push on a Friday since upgrading to R80.20 on the Management Server. Monday afternoon some phones started having issues. At first I thought it was coincidental. Coincidences rarely happen though. SmartConsole Logging wasn’t reporting any drops.

How can a change delay days?

In our environment, instead of having CheckPoint rematch ACLs on Policy push, we accept all previously trusted connections. This helps avoid connections resetting after a policy push.

CheckPoint Keep All Connections

With this, already trusted TCP connections were allowed but new ones were being prevented and it took a few days for some of the phones to reset/reconnect and get blocked.


We log all traffic and blocks but this one was not reporting as dropped

I was even using the “fw ctl zdebug + drop” command and it reported no drops. SmartConsole reported it even accepting the TCP/1720 packet but it simply did not get routed from the ingress interface to egress interface.

I verified this by running tcpdump on the CheckPoint as well as further down machines and I could see the CheckPoint receiving the TCP/1720 but then went into a black hole.

The Fix

I was all set to enable H.323 Debugging when I came across this article and found it. Specifically this section

Documentation - Allow an initiation of H.323 connections from server to endpoints

From all of my packet tracing this was the case. The Phones could register via UDP/1719 but when the GateKeeper would try to connect back to the phones over TCP/1720 the firewall accepted it but something else in CheckPoint was blocking it so it had to be H.323 inspection.

I went ahead and enabled this and bam, it started working!

Setting - Allow an initiation of H.323 connections from server to endpoints

Just add this to the list of fun nuances. I believe R77 was just more relaxed in this case about the inspection and in R80 they have tightened it up a bit.

Author: David Chapman

I started my IT career in the very late 1990's as a systems administrator for a benefits company. I have always enjoyed learning new technologies and helping people fix problems which has lead me through a few different positions over the past 20+ years.