[Asterisk-Users] internal & external SIP

[Jon Lawrence]

Hi all,
I've got a problem with external sip clients.
My * box has 2 nics, one to my internal network and one on a public IP.
There are external sip clients (on public IPs) and internal clients on the 
internal nic.
both clients can register fine.
I can phone external clients from the internal clients and the connection 
works perfectly.
But if an external client phones an internal one, the internal phone rings, 
but when the phone is picked up the external call disappears.
Both internal and external have canreinvite=no

Can anyone give me any ideas where to start looking into this.

Regards,
Jon