I have an OpenBSD 3.7 gateway. This gateway run Asterisk. I have two windows box which use X-Lite softphone, and each box connect to Asterisk using this softphone (X-Lite). Asterisk use the following configuration : /etc/asterisk/sip.conf ; Phone #1 [Phone1] type=friend host=dynamic nat=yes defaultip = 192.168.10.12 # windows box IP context = sip callerid="Phone1" <1> ; Phone #2 [Phone2] type=friend host=dynamic nat=yes defaultip = 192.168.10.5 # second windows box IP context = sip callerid="Phone" <2> i have the following extension : /etc/asterisk/extensions.conf [sip] exten => 1,1,Dial(SIP/Phone1,20,tr) exten => 2,1,Dial(SIP/Phone2,20,tr) One windows box have phone number "1" and the other windows box have phone number "2". I call Phone number 2 from Windows box with phone number 1 and work. The first session started (Windows box 1 call Windows Box2 ) , i talk on windows box 1 and i hear my voice on Windows box2. I close this phone session. I start a new session (Windows box1 call again Windows Box 2), i talk but now i don't hear my voice on windows box 2. I think this is a NAT issue . I don't hear my voice again until i restart Asterisk :( Any idea to help me ? Thank you very much !