[Asterisk-Users] NAT and SIP

[Rich Adamson]

> > For example, the first sip session will use udp 5060, but on weird
> > nat boxes the second sip session will get mapped to udp 5061 (or 
> > something like that), and obviously * isn't listening on that port.
> 
> 
> The port that shows up in "sip show peers" is the remote SOURCE port 
> and addresss.  Asterisk does not normally care about such things.  Any 
> NAT router that modified the DESTINATION port and address would not 
> not work.
> 
> Does anyone know of a basic NAT for Dummies document that I can point 
> people to?  This is something that comes up again and again from 
> people that don't understand how NAT works.

I'm not aware of any good Dummies doc. Lots of bits and pieces around,
but nothing very complete.

I'd suspect that part of the reason for that is the substantial variation
in how nat is actually implemented in cheap commercial boxes (firewalls, 
dsl modems, etc). Not at all consistent with any reasonable definition
of nat.