Alex, thank you for the answer, I have installed rtpproxy and is running: rtpproxy -l 66.152.18.221 -s udp:localhost:7722 this is my NAT kamailio.cfg: #!ifdef WITH_NAT # ----- rtpproxy params ----- modparam("rtpproxy", "rtpproxy_sock", "udp:127.0.0.1:7722") # ----- nathelper params ----- modparam("nathelper", "natping_interval", 30) modparam("nathelper", "ping_nated_only", 1) modparam("nathelper", "sipping_bflag", FLB_NATSIPPING) modparam("nathelper", "sipping_from", "sip:pinger@kamailio.org") # params needed for NAT traversal in other modules modparam("nathelper|registrar", "received_avp", "$avp(RECEIVED)") modparam("usrloc", "nat_bflag", FLB_NATB) #!endif And in the route(NAT) I have changed the nat test: * if (!nat_uac_test("32"))* This is because I want to do NAT only with those clients which source signalling is not RFC1918 compliant. Since I'm using a transparent proxy on the public ip. The problem I'm still having is that the RTP traffic are routing to the private ip address of the sip phone. I have been with this since a couple of days and I would appreciate a little help. Thanks ons advance, Lucas On Tue, May 31, 2011 at 2:45 PM, Alex Balashov <abalashov(a)evaristesys.com>wrote;wrote: