[Asterisk-Users] NAT and SIP

[Rich Adamson]

> So this leads me to believe there's some kind of limit per IP on 
> NAT'ed SIP clients.

> Can anybody shed some light on this?

It sounds like a nat box issue and probably related to port mapping.

I've seen the same kind of issue with multiple vpn clients trying to
pass through a single nat box. Swapping the box for a different model
fixed the problem.

The only way to tell for sure is to trace the packets inside and
outside the nat box to see exactly what the box is doing.

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.