Hey Guys, We're trying to use an OpenSER server for some SIP communications. While it works great for most scenarios (Behind NAT, Outside of NAT, One client behind NAT and the other Outside of NAT), there is one that seems to be causing difficulty (naturally, this is the one that is being requested. :\ ). I'm being asked if we can set up the server to not only support the previously mentioned scenarios but also where both clients are behind the same NAT, but no ports are forwarded through the NAT for the clients. Basically, client calls another client on the same network using the off-network server as a registrar (no Mediaproxy or RTPproxy). Is this even possible with OpenSER (v 1.0.1)? If so, perhaps I'm doing something wrong in my config (pertinent parts attached below). I know this part of the config works for most situations, so long as the clients have ports routed in the firewall/NAT device (minus the use of AVP at the end to try and achieve the desired results). Any help at all would be appreciated. Justin Pearce route{       # Label all transactions for accounting, as per the       # parameters for the Accounting Module       setflag(1);       setflag(2);       setflag(3);       setflag(4);       # initial sanity checks -- messages with       # max_forwards==0, or excessively long requests       if (!mf_process_maxfwd_header("10")) {             sl_send_reply("483","Too Many Hops");             exit;       };       #If the message is too big for SIP       if (msg:len >=  2048 ) {             sl_send_reply("513", "Message too big");             exit;       };       # We record-route all messages -- to make sure that       # subsequent messages will go through our proxy; that's       # particularly good if upstream and downstream entities       # use different transport protocol       if (!method=="REGISTER"){                  record_route();         };       # Subsequent messages withing a dialog should take the       # path determined by record-routing       if (loose_route()) {             # mark routing logic in request             append_hf("P-hint: rr-enforced\r\n");             route(1);       };       if (!uri==myself) {             # mark routing logic in request             append_hf("P-hint: outbound\r\n");             route(1);       };       # if the request is for other domain use UsrLoc       # (in case, it does not work, use the following command       # with proper names and addresses in it)       if (uri==myself) {                             if (method=="REGISTER") {                        fix_nated_register(); # Fix REGISTERs broken by NAT                    fix_nated_contact();                    force_rport(); # Force the return port in the firewall                    add_rcv_param(); # Add the "recieved" parameter to the location                        save("location"); # Save the location in the registrar                        acc_db_request("200", "acc"); # Log the 200 OK                        exit;             };             lookup("aliases"); # Check the ALIASES table             if (!uri==myself) {                   append_hf("P-hint: outbound alias\r\n");                   route(1);             };             # native SIP destinations are handled using our USRLOC DB             if (!lookup("location")) {                   # If the user cannot be found, reply to the user                   # and exit the call process                   sl_send_reply("404", "Not Found");                   exit;             };             append_hf("P-hint: usrloc applied\r\n");       }else{       # if the request is for other domain use UsrLoc       # (in case, it does not work, use the following command       # with proper names and addresses in it)             if (method=="REGISTER") {                   fix_nated_register(); # Fix the REGISTERs broken bt NAT                   fix_nated_contact();                   force_rport(); # Force the return port in the firewall                   add_rcv_param(); # Add the "recieved' parameter to the location                   save("location"); # Save the location in the registrar                   acc_db_request("200", "acc"); # Log the 200 OK                   exit;              };             # native SIP destinations are handled using our USRLOC DB             if (!lookup("location")) {                   # If the user cannot be found, notify sender and exit.                   sl_send_reply("404", "Not Found");                     exit;                 };       };       # Continue onto route #1 below...       route(1); } route[1] {       avp_write("$src_ip", "s:temp_from_ip");       avp_write("$duri", "s:temp_to_ip");       avp_subst("s:temp_to_ip", "/^\D+@//i");       if(method=="INVITE" && !(to_uri=~"^admin@[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+[:]*[0-9]*")){           fix_nated_contact();         force_rport();           if(avp_check("s:temp_to_ip", "ne/s:temp_from_ip/g")){         fix_nated_sdp("15");         }else{             append_hf("P-Hint: Same Domain");         };         record_route();              };       #This is set of processes to be preformed on all replies...         #This conditional is to try and redeem ACKs that some how managed to get a private address attached to them.         #This is basically a hack to try and "normalize" the packets coming through and pray they work.    if(method=="ACK" || method=="BYE" || method=="INFO"){  if(uri=~"^sip:192\.168\.[0-9]+\.[0-9]+[:]*[0-9]*" || uri=~"^sip:10\.[0-9]+\.[0-9]+\.[0-9]+[:]*[0-9]*" || uri=~"^sip:172\.(16|17|18|19|20|21|22|23|24|25|26|27|28|29|30|31)\.[0-9]+\.[0-9]+[:]*[0-9]*"){                 #Rewrite the R-URI of the packet to the To-URI in the To header.                  subst_uri('/^sip:[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+[:]*[0-9]*$/$tu/ig');                 #Force the server to perform a lookup on the new URI and try and route it properly.                  lookup("location");           };         };       # send it out now; use stateful forwarding as it works reliably       # even for UDP2TCP       if (!t_relay()) {             # If the stateful relay of a message cannot take place,             # reply to the sender statelessly with the error.             sl_reply_error();       };       exit; } onreply_route{         if(status=="200" || method=="INVITE"){       fix_nated_contact();       force_rport();       if(!search("P-Hint: Same Domain")){           fix_nated_sdp("15");          };        }; }