Hi list! Today I tried to change the NAT-configuration on my Firewall to use another port for SIP. I configured it so: /sbin/iptables -t nat -A PREROUTING -p udp -m udp --dport 10000:10100 -j DNAT --to-destination 192.168.20.120 /sbin/iptables -t nat -A PREROUTING -p udp -m udp --dport <my new port> -j DNAT --to-destination 192.168.20.120:5060 then, I tried to log on my Asterisk with my mobile phone. It works. Great! Then I tried to call an extension I created for the tests. This extension just play a beep, record a message and play it back. I hear the beep and I can speak my test message, then I can just hear a couple of seconds of my message and I get this error: [Jun 9 07:41:56] WARNING[19374] chan_sip.c: Retransmission timeout reached on transmission 1ec8759e5160b42b92000629ec5e4771 at 10.102.46.147 for seqno 993 (Critical Response) -- See https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions Packet timed out after 13569ms with no response [Jun 9 07:41:56] WARNING[19374] chan_sip.c: Hanging up call 1ec8759e5160b42b92000629ec5e4771 at 10.102.46.147 - no reply to our critical packet (see https://wiki.asterisk.org/wiki/display/AST/SIP+Retransmissions). I'm really not sure, what can be the problem, now... I read the wiki page, but I can understand what is wrong now in a configuration that works for days... Have I to say Asterisk, that the NAT receive data from another port? This is the only change in my configuration since yesterday, as all worked... Thanks Luca Bertoncello (lucabert at lucabert.de)