If your equipment supports STUN then you should enable and use the following address for the stun server :
sip.nehos.com.au and port 5060 or cpbx.nehos.com.au and port 5060
Please note that our STUN server uses the same IP and port as the main SIP Proxy. This allows for a much better NAT traversal than other solutions that have STUN on a different IP and port than the main proxy.
SIP OPTIONS should be turned off on your equipment. If our network detects your equipment is behind a NAT it will automatically send your equipment SIP OPTIONS requests to keep your NAT ports open for inbound traffic from our network.
Application Layer Gateways (ALGs) need to be turned off on your router if it is supported. Most vendor ALG’s break SIP NAT traversal.
Asterisk supports stun and can be enabled by editing the res_stun_monitor.conf as follows
[general]
stunaddr = sip.nehos.com.au:5060
or
stunaddr = sip.nehos.net:5060