[SR-Users] Cannot run Kamailio on public IP

Hello all, I have installed latest Kamailio 3.1.3 on latest ubuntu server. Everything seems to be working well on my LAN. I can successfully register with local Kamailio IP address (192.168.1.137). The issue is that I can not run Kamailio on my public IP: listen=udp:77.XX.XX.XX:5060 listen=udp:192.168.1.137:5060 port=5060 Kamailio runs behind Linksys WRT54GL router with latest Linksys firmware and DMZ is turned on (192.168.1.137). Here is the error I am getting when trying to run kamailio with my public IP: Apr 7 02:57:40 sipbox kamailio[1050]: ERROR: <core> [udp_server.c:400]: ERROR: udp_init: bind(7, 0x82cc6e4, 16) on 77.XX.XX.XX: Cannot assign requested address Do you have any idea what I'm doing wrong ? Thanks !