[Linphone-developers] Two Linphones behind same NAT

[Conrad Beckert]

Hi,

We run an Asterisk server at the office we connect our phones to. I have a 
small network at home which shares a single internet connection by a NAT 
router.

Linphone works like a charme in this environment (which includes an SIP ATA 
box for analog phones) unless I open it on more than one machine. If I do so, 
I can still issue calls but recieving calls fails -> no sound (interestingly 
video works) there is also no counfusion about the signalling.

Anyway. The reason seems to be that unlike other softphones Linphone occupies 
fixed UDP ports for SIP signalling and RTP. So I changed those ports in the 
config and everything was fine.

Actually - I came to this idea because I deal a lot with VoIP and NAT (on H323 
with all the Netmeetings, OpenPhones, etc..) 

1.
Anyway - it seems to be that dynamic allocation of RTP ports - despite its 
unfriendlyness to firewalls has its advantages (at least to be able to give a 
range to chose from)


2. 
Before the software can handle this, we should put this info in the FAQ of the 
website. :-) 

Greetings from Berlin
Conrad