If you are using two or more Ethernet interfaces on your PiaF server, you can direct SIP or IAX2 traffic out a specific interface by adding the following command to sip_general_custom.conf or iax_general_custom.conf:
bindaddr=“IP address of Ethernet interface”
e.g. This sends SIP traffic only out this port
This sends out IAX traffic out a separate port
Or you can send all VoIP traffic out one port and data traffic out the other. Note that the two ports should be on separate networks.