Panoramisk / The VoIP druid 

One of the main issue with SIP is that NAT traversal is a nightmare. When you connect to your corporate network using a VPN, it is not easy to use a sip hard phone. Using a softphone is, in general, the simplest way.

However a small tool really useful can help you: Siproxd

Siproxd is a Sip proxy really simple to use. After a standard installation (depending of your distribution) you can start to configure it. Three parameters must be modified:

• if_inbound: used to define the network interface used as internal network. It’s the network where your sip phone is plugged (eth0 for example)
• if_outbound: used to define external network interface. In my case it is the VPN’s virtual network interface (tap0 for example)
• hosts_allow_reg: list of networks allowed to register to a SIP server.

Now you have a fully functional Sip proxy. Adding debug log (silence_log parameter) can help you for diagnostic.

Finally only a Microsoft Windows port is missing…

Project web : siproxd