In order to run your own SIP forwarding daemon, there are two things to consider:
- IP address: it is advised to explicitly bind the daemon to a specific IP (or IPv6) address using the -b command line option.
- DNS: in order to have SIP requests for example.com routed to your SIP forwarding server, you will either have to set up your DNS zone such that A/AAAA records for example.com point to the SIP forwarding server, or add an SRV record for _sip._udp.example.com.
As an example, have a look at the setup for the cmeerw.org domain which has a SRV record:
_sip._udp.cmeerw.org. 28800 IN SRV 10 0 5060 edge.cmeerw.net.
and A/AAAA records for edge.cmeerw.net:
edge.cmeerw.net. 28800 IN A 217.11.63.119 edge.cmeerw.net. 28800 IN AAAA 2001:6f8:131c::1
Consequentially, the SIPFwd daemon is bound to these IP addresses using the the -b command line option:
sipfwd -b 217.11.63.119 -b 2001:6f8:131c::1