Hi Bogdan, and sorry for my stupid question :) Let's try to describe the complete scenario We're a VoIP provider using OpenSER as registrar server and load balancer (with dispatcher module) for a cluster of Asterisk servers We're now talking of received calls from our users perspective. One of our Asterisks originate an INVITE for someuser@openser, OpenSER does a lookup in the location table and forward the INVITE statefully. When the user answer the call sends a 200 OK to OpenSER which is forwarded to Asterisk, Asterisk sends back an ACK which is not forwarded back to the user. The user retries to send the OK but after a while it drops the call because it's considering that a critical error Here is a dump of what I mean ASTERISK -> OPENSER - SIP/SDP Request: INVITE - SIP:sorsatrav@213.92.79.131, with session description OPENSER -> ASTERISK - SIP Status: 100 trying -- your call is important to us OPENSER -> USER - SIP/SDP Request: INVITE - SIP:s@81.196.154.44:5060, with session description OPENSER -> USER - SIP/SDP Request: INVITE - SIP:s@81.196.154.44:5060, with session description USER -> OPENSER - SIP Status: 100 Trying USER -> OPENSER - SIP/SDP Status: 200 OK, with session description OPENSER -> ASTERISK - SIP/SDP Status: 200 OK, with session description ASTERISK -> OPENSER - SIP Request: ACK - SIP:s@192.168.0.251 (this packet is not forwarded to user so client retries to send the OK) USER -> OPENSER - SIP/SDP Status: 200 OK, with session description OPENSER -> ASTERISK - SIP/SDP Status: 200 OK, with session description ASTERISK -> OPENSER - SIP Request: ACK - SIP:s@192.168.0.251 In this case the USER is an Asterisk, I tried the same tests with an XLite as user and the packet is forwarded correctly. Here are the details of the ACK packet Request-Line: ACK sip:s@192.168.0.251 SIP/2.0 Message Header Via: SIP/2.0/UDP 213.92.79.138:5060;branch=z9hG4bK5a1555e7;rport Route: <sip:213.92.79.131;lr=on;ftag=as3b66b2ad> From: "Unknown" <sip:Unknown@213.92.79.138>;tag=as3b66b2ad To: <sip:sorsatrav@213.92.79.131>;tag=as4b185fcc Contact: <sip:Unknown@213.92.79.138> Call-ID: 6c21caa9503939325dc45a343434e8dc(a)213.92.79.138 CSeq: 102 ACK User-Agent: Exsorsa Max-Forwards: 70 Content-Length: 0 Tnx in advance for you help Regards Edoardo P.S.: Here is my openser.cfg # $Id: ser.cfg,v 1.21.4.1 2003/11/10 15:35:15 andrei Exp $ # ----------- global configuration parameters ------------------------ check_via=yes # (cmd. line: -v) dns=no # (cmd. line: -r) rev_dns=no # (cmd. line: -R) fifo="/tmp/ser_fifo" #uid=nobody #gid=nobody # ------------------ module loading ---------------------------------- loadmodule "/usr/lib/openser/modules/sl.so" loadmodule "/usr/lib/openser/modules/tm.so" loadmodule "/usr/lib/openser/modules/rr.so" loadmodule "/usr/lib/openser/modules/maxfwd.so" loadmodule "/usr/lib/openser/modules/usrloc.so" loadmodule "/usr/lib/openser/modules/registrar.so" loadmodule "/usr/lib/openser/modules/nathelper.so" loadmodule "/usr/lib/openser/modules/textops.so" loadmodule "/usr/lib/openser/modules/exec.so" loadmodule "/usr/lib/openser/modules/uri.so" loadmodule "/usr/lib/openser/modules/uri_db.so" loadmodule "/usr/lib/openser/modules/dispatcher.so" loadmodule "/usr/lib/openser/modules/mysql.so" loadmodule "/usr/lib/openser/modules/auth.so" loadmodule "/usr/lib/openser/modules/auth_db.so" modparam("usrloc", "db_mode", 2) modparam("usrloc", "db_url", "mysql://user:pass@192.168.252.5/openser") modparam("usrloc", "timer_interval", 120) modparam("auth_db", "calculate_ha1", 0) modparam("auth_db", "db_url", "mysql://user:pass@192.168.252.5/db") modparam("uri_db", "db_url", "mysql://user:pass@192.168.252.5/openser") modparam("rr", "enable_full_lr", 1) modparam("registrar", "nat_flag", 6) modparam("registrar", "max_expires", 3600) modparam("registrar", "min_expires", 60) modparam("registrar", "append_branches", 0) modparam("registrar", "desc_time_order", 1) modparam("nathelper", "natping_interval", 20) # Ping interval 20 s modparam("nathelper", "ping_nated_only", 1) # Ping only clients behind NAT modparam("dispatcher", "force_dst", 1) # ------------------------- request routing logic ------------------- # main routing logic route{ if (!mf_process_maxfwd_header("10")) { sl_send_reply("483","Too Many Hops"); exit; }; if ( msg:len > max_len ) { sl_send_reply("513", "Message too big"); exit; }; if ( (method=="OPTIONS") || (method=="SUBSCRIBE") || (method=="NOTIFY") ) { sl_send_reply("405", "Method Not Allowed"); exit; } if (!method=="REGISTER") { record_route(); }; if ((src_ip==ip.of.asterisk.1) || (src_ip==ip.of.asterisk.1)) { if (!lookup("location")) { sl_send_reply("486", "Busy here"); exit; }; if (!t_relay()) { sl_reply_error(); }; exit; }; if (nat_uac_test("3")) { if ((method=="REGISTER") || (method=="INVITE") || (method=="OPTIONS")) { fix_nated_contact(); force_rport(); setflag(6); # Mark as NATed } } if (method=="REGISTER") { if (!proxy_authorize("exorsa", "openser_view")) { proxy_challenge("exorsa", "0"); exit; } if (!check_to()) { sl_send_reply("403", "Digest username and URI username do NOT match! Stay away!"); exit; } save("location"); exit; }; if (method=="INVITE") { if (!proxy_authorize("exorsa", "openser_view")) { proxy_challenge("exorsa", "0"); exit; } if (!check_from()) { sl_send_reply("403", "Digest username and URI username do NOT match! Stay away!"); exit; } } # loose-route processing if (loose_route()) { # mark routing logic in request append_hf("P-hint: rr-enforced\r\n"); t_relay(); exit; }; if (!uri==myself) { # mark routing logic in request append_hf("P-hint: outbound\r\n"); route(1); exit; }; append_hf("P-hint: usrloc applied\r\n"); route(1); } route[1] { # !! Nathelper if (uri=~"[@:](192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[0-1])\.)" && !search("^Route:")){ sl_send_reply("479", "We don't forward to private IP addresses"); exit; }; # NAT processing of replies; apply to all transactions (for example, # re-INVITEs from public to private UA are hard to identify as # NATed at the moment of request processing); look at replies t_on_reply("1"); if ((src_ip!=ip.of.asterisk.1) && (src_ip!=ip.of.asterisk.2)) { ds_select_dst("1", "0"); } if (!t_relay()) { sl_reply_error(); }; } # !! Nathelper onreply_route[1] { # NATed transaction ? if (isflagset(6) && status =~ "(183)|2[0-9][0-9]") { fix_nated_contact(); # otherwise, is it a transaction behind a NAT and we did not # know at time of request processing ? (RFC1918 contacts) } else if (nat_uac_test("1")) { fix_nated_contact(); }; } Bogdan-Andrei Iancu ha scritto: