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Advertise your Public IP in your SIP Signaling on Asterisk-based PBXs

This article describes advertising your public IP in your SIP signaling on Asterisk-based PBXs. If your Asterisk-based PBX is behind NAT or is advertising a private IP, such as, in your SIP signaling, then you'll need to make the following changes to prevent intermittent one-way audio and other call issues. 

NOTE: The following example assumes that your Asterisk PBX uses the IP address 192.168.1.x.
Before you begin
  • You will need two firewall policies for Flowroute's Direct Media set up on your router to prevent call and audio issues. 

To advertise your public IP:
  1. Go to /etc/asterisk/.
  2. Using a text editor, open sip.conf.
  3. Modify the file with the following: 


      where is your public IP address. This can be found on the router's administration web page or by going to, which will read and display your IP address. 

    • localnet= 

      This must match your local subnet. 

    • nat=yes 

  4. Restart Asterisk. 

    Consult your PBX documentation on how to perform this. Many PBXs can restart Asterisk by running the following commands: 

    service restart asterisk 

    sudo /etc/init.d/asterisk restart 

  5. Verify that the firewall rules were set up.