•Two new NAT options, auto_force_rport and auto_comedia, have been added which set the force_rport and comedia options automatically if Asterisk detects that an incoming SIP request crossed a NAT after being sent by the remote endpoint.
•NAT settings are now a combinable list of options. The equivalent of the deprecated nat=yes is nat=force_rport,comedia. nat=no behaves as before.
Asterisk 1.8:
The 'nat' option has now been been changed to have yes, no, force_rport, and comedia as valid values. Setting it to yes forces RFC 3581 behavior and enables symmetric RTP support. Setting it to no only enables RFC 3581 behavior if the remote side requests it and disables symmetric RTP support. Setting it to force_rport forces RFC 3581 behavior and disables symmetric RTP support. Setting it to comedia enables RFC 3581 behavior if the remote side requests it and enables symmetric RTP support.
