Navigate to NETWORK | VoIP > Settings| H.323 Settings.
Choose whether to enable H.323 transformation globally or by firewall rule:
Use global control to enable H.323 Transformations. This option is selected by default.
Use firewall Rule-based control to enable H.323 Transformations. Be sure to configure a firewall rule to control H.323 transformations.
If you are not configuring H.323 transformations, go to Step 5.
Select Enable H.323 Transformation to allow stateful H.323 protocol-aware packet content inspection and modification by the firewall. This option is disabled by default. When the option is selected, the other H.323 options become active.
The firewall performs any dynamic IP address and transport port mapping within the H.323 packets, which is necessary for communication between H.323 parties in trusted and untrusted networks/zones.
Disable the Enable H.323 Transformation to bypass the H.323 specific processing performed by the firewall.
Select Only accept incoming calls from Gatekeeper to ensure all incoming calls go through the Gatekeeper for authentication. The Gatekeeper refuses calls that fail authentication.
In the H.323 Signaling/Media inactivity time out (seconds) field, specify the amount of time a call can be idle before the firewall blocks further traffic. A call goes idle when placed on hold. The default time is 300 seconds (5 minutes), the minimum time is 60 seconds (1 minute), and the maximum time is 122400 seconds (34 hours).
The Default WAN/DMZ Gatekeeper IP Address field has a default value of 0.0.0.0. Enter the default H.323 Gatekeeper IP address in this field to allow LAN-based H.323 devices to discover the Gatekeeper using the multicast address 188.8.131.52. If you do not enter an IP address, multicast discovery messages from LAN-based H.323 devices go through the configured multicast handling.