• Your firewall is blocking the application because fragmented packets are sent from the PBX. 

Fragmented packets - FIREWALL / example Agnitum Outpost

Telephone system functions such as "Busy Lamp Field" (BLF) and "Presence" need more data volume. Information are send as XML data between the devices. Depending on how large those data are, they are split into several UDP packages. The packets are fragmented.

The 3CX Phone System for example, sends quite a lot of information in short intervals. In combination with the Agnitum firewall (Outpost), all fragmented UDP packets will be rejected because the firewall consider that all such packet are potentially unsafe. Unfortunately Outpost does not allow the user to create the necessary rules by using the Graphical Interface.

Solution for Agnitum Outpost Firewall:

1. Disable Self-Protection mode by right-clicking on system tray icon and selecting 'Disable Self-protection'.
2. Shutdown Outpost by right-clicking on the program icon in the system tray and selecting 'Exit'.
3. Open the following file: C:\Program Files\Agnitum\Outpost Firewall Pro\machine.ini C:\Program Files\Agnitum\Outpost Security Suite Pro\machine.ini If you can't see extensions of these files, please, open "Start - Control Panel - Folder options - View" and untick "Hide extensions for known filetypes". All extensions will now be visible to you.
4. Find section "; block no-first fragments arrives before first fragment".
5. Change the value of the parameter 'BlockNoOrderedFragment' to 'no'.
6. Save changes.
7. Start Outpost and enable Self-protection mode.

TIP: Normally you receive an information from your Firewall when fragmented packets are blocked. If your firewall does not support configuring a rule for that issue, then do not hesitate to contact the manufacturer. Often they have invisible settings in INIs etc, like our example above.