How do i fix one-way audio on my Asterisk PBX?

The following is used to fix one way audio on your Asterisk PBX if you do not have a public static IP address on your asterisk pbx, and you are using IP authentication (not SIP username/password Registration).

You will need to enter the following two settings (externip and localnet) at the top of your sip.conf file in the general section. 

externip=WAN IP address

localnet= (or whatever your private LAN is configured for)

Depending on your setup, you might need to forward all ports to your Asterisk server's private IP address or put the private IP address of the Asterisk server on the DMZ. 

Note: If you have a public static IP address assigned to the server itself, then you do not need to add these settings to your config.