3CX (Phone System) calls are disconnecting randomly

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3CX (Phone System) calls are disconnecting randomly

L1 Bithead

Dear Community Team,


One of the customer is facing issues on 3CX call system after upgrading to new firewall PA-3220 recently. It was Forcepoint Firewall used by the customer earlier and working fine.


Note: 3CX is a software-based private branch exchange based on the SIP standard.



  • 3CX server has been hosted outside with public IP directly. 
  • Users are behind the PA firewall using application to connect 3CX and make and receive calls.
  • In PA, Many to one NAT configured to access 3CX server.



  • Users are unable to hear the audio from incoming sometime.
  • Calls are getting disconnected randomly.




  • Allowed any application and any ports without any security profiles, but still the issues are occurring.
  • Disabled ALG in SIP, but same.


I would need any expert suggestions ASAP.






L1 Bithead

It was resolved after increasing session timeout in service ports.




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