Home / ClearlyIP Gateways / Failover Gateway - GWSAK / Typical Use Cases / FXS Gateway To a PBX with 4G Failover

FXS Gateway To a PBX with 4G Failover


  • We will setup this gateway to just register to your PBX with each of the 6 FXS ports registered to the PBX with a different Extension Number and SIP Password.
  • If the internet goes down the Gateway will failover to using the 4G connection to stay connected to your PBX.
  • The setup guide below assumes you have already setup the 4G Sim and APN as outlined in our Initial Setup guide here

Define How to Reach your PBX

  • The gateway needs to be told what the IP or FQDN of your PBX that you want to register the FXS ports to.
  • Navigate to Outbound Calling.

  • Set the following fields and make sure you save your changes when done.
    • Cloud PBX - The IP address or FQDN of your PBX.
    • Local Signaling Port  - The SIP signaling port of your PBX--usually 5060.
    • Options Request Interval - The gateway will periodically send SIP OPTIONS messages to verify whether not the PBX is reachable. We recommend something between 15-30 seconds. If its unreachable on the Local LAN this will trigger the failover to using 4G.  When the PBX is reachable, service will restore back to the LAN from 4G.

  • Press the Save button when done

Map FXS Ports to your PBX as Extensions

  • Navigate to Extensions > Analog

  • You will see the 6 FXS ports listed.  Ports 1, 2, 5, 6, 7, 8.  Ports 3 and 4 wont be listed here as they are FXO ports.

  • Click on the field under Mode for which port you want to setup as a Extension from your PBX and set it to be Cloud PBX.

  • Set the following fields based on what you have setup in your PBX for this extension.
    • Number - Extension Number you are registering this port as to your PBX.
    • Registration - Check the Enable button
    • Username - Extension Number you are registering this port as to your PBX.
    • Password - The SIP Secret for the extension from your PBX that you are registering as.

  • Press the Save button when done

  • The Port(s) should now show Register Success under Status.

Setup STUN Server for NAT

     RSS of this page