[asterisk-users] Multi-homed SIP in Asterisk 11?

[Gareth Blades]

On 31/07/13 16:12, Tony Mountifield wrote:
> Thanks. But I thought localnet= and externip= were for when the external
> interface is going through NAT. In this case the ITSP is connected through
> a real non-NATted public interface.
>
> Is it possible to specify directmedia=no just for the SIP trunk? So that
> the phones could still do direct media between themselves, but not if
> they were connected to the trunk?
>
> Cheers
> Tony

The localnet= can have implications as when asterisk sees that IP 
address it knows its local. This may have knock on effects when you have 
other settings which do different things of the endpoint is known to be 
behind nat.

Its not clearly documented what needs to be set when directmedia=no is 
turned on. Does it only need to be set on one endpoint, both, or just 
the destination etc... I am sure you can do it that way but you will 
need to have a play and work it out.

I wonder if using directmedia=nonat will help at all. It will disable 
directmedia if one endpoint is behind nat (this is where localnet= comes 
in) but I dont know if it will then know to enable direct media if both 
endpoints are behind nat. I suspect it wont as the endpoints may not 
necessarily be behind the same nat so this would be unsafe.