debug=9
    fork=yes
    log_stderror=no

    listen=192.168.20.1
    port=5060
    children=4
    server_signature=no
    dns=no
    rev_dns=no
    disable_tcp=yes

    alias="192.168.20.1"

    check_via=no
    syn_branch=yes

    sip_warning=no      /* noisy feedback */
    fifo_mode=0666
    fifo="/tmp/ser_fifo"
    fifo_db_url="mysql://ser:heslo@192.168.20.2/ser"

    # ------------- external module loading
    loadmodule "/usr/local/lib/ser/modules/mysql.so"
    loadmodule "/usr/local/lib/ser/modules/sl.so"
    loadmodule "/usr/local/lib/ser/modules/tm.so"
    loadmodule "/usr/local/lib/ser/modules/rr.so"
    loadmodule "/usr/local/lib/ser/modules/maxfwd.so"
    loadmodule "/usr/local/lib/ser/modules/usrloc.so"
    loadmodule "/usr/local/lib/ser/modules/registrar.so"
    loadmodule "/usr/local/lib/ser/modules/mediaproxy.so"
    loadmodule "/usr/local/lib/ser/modules/nathelper.so"
    loadmodule "/usr/local/lib/ser/modules/auth.so"
    loadmodule "/usr/local/lib/ser/modules/auth_db.so"
    loadmodule "/usr/local/lib/ser/modules/acc.so"
    loadmodule "/usr/local/lib/ser/modules/group.so"
    loadmodule "/usr/local/lib/ser/modules/print.so"
    loadmodule "/usr/local/lib/ser/modules/textops.so"
    loadmodule "/usr/local/lib/ser/modules/uri.so"
    loadmodule "/usr/local/lib/ser/modules/uri_db.so"
    loadmodule "/usr/local/lib/ser/modules/domain.so"
    loadmodule "/usr/local/lib/ser/modules/options.so"
    loadmodule "/usr/local/lib/ser/modules/avpops.so"
    loadmodule "/usr/local/lib/ser/modules/permissions.so"
    loadmodule "/usr/local/lib/ser/modules/diversion.so"
    loadmodule "/usr/local/lib/ser/modules/xlog.so"

    # ------------- db_url setting
    modparam("acc|auth_db|domain|group|permissions|uri_db|usrloc", "db_url", "mysql://ser:heslo@192.168.20.2/ser")

    # ------------- use_domain setting
    modparam("auth_db|group|registrar|uri_db|usrloc", "use_domain", 0)

    # ------------- domain parameters
    modparam("domain", "db_mode", 1)

    modparam("registrar", "min_expires", 600)
    modparam("registrar", "max_expires", 3600)
    modparam("registrar", "default_expires", 600)
    modparam("registrar", "default_q", 100)
    modparam("registrar", "nat_flag", 6)

    modparam("rr", "enable_full_lr", 0)

    modparam("tm", "fr_timer", 30)
    modparam("tm", "fr_inv_timer", 60)
    modparam("tm", "wt_timer", 10)
    modparam("tm", "fr_inv_timer_avp", "inv_timeout")

    modparam("usrloc", "db_mode", 2)
    modparam("usrloc", "timer_interval", 60)
    modparam("usrloc", "desc_time_order", 0)

    # -------------- AVPOPS parameters
    modparam("avpops", "avp_url", "mysql://ser:heslo@192.168.20.2/ser")

    modparam("avpops", "avp_table", "usr_preferences")
    modparam("avpops", "avp_aliases", "temp=i:36")

    route {

        if (!mf_process_maxfwd_header("10")) {
            sl_send_reply("483", "Too Many Hops");
            break;
        };

        if (msg:len > max_len) {
            sl_send_reply("513", "Message Too Large");
            break;
        };


        # ------------- Record route all non REGISTER messages
        if (method=="INVITE" && client_nat_test("3")) {
          record_route_preset("192.168.20.1:5060;nat=yes");
        } else if (method!="REGISTER") {
            record_route();
        };


        # -------------- end_media_session() tears down call
        if (method=="BYE" || method=="CANCEL") {
            end_media_session();
            setflag(1);
            setflag(2);
        };

        if (loose_route()) {
            if (has_totag() && (method=="INVITE" || method=="ACK")) {
               if (client_nat_test("3") || search("^Route:.*;nat=yes")) {
                  setflag(6);
                  use_media_proxy();
               };
            };
            append_hf("P-hint: Loose Routed\r\n");

            route(1);
            break;
        };

        if (uri!=myself) {
            append_hf("P-hint: External Destination\r\n");
            route(4);
            route(1);
            break;
        };

        if (uri==myself) {
            append_hf("P-hint: Local Destination\r\n");
            if (method=="ACK") {
                route(9);
                break;
            } else if (method=="CANCEL") {
                route(5);
                break;
            } else if (method=="INVITE") {
                setflag(1);
                setflag(2);
                route(5);
                break;
            } else if (method=="REGISTER") {
                route(3);
                break;
            } else if (method=="OPTIONS") {
                options_reply();
                break;
            } else if (method=="REFER") {
                route(5);
                break;
            } else if ((method=="SUBSCRIBE") || (method=="PUBLISH") || (method=="MESSAGE")) {

                  if ((method=="MESSAGE") && (src_ip==192.168.20.3)) {
                     route(8);
                     break;
                  };

                  if (!t_newtran()) {
                     xlog("L_ERR", "newtran error\n");
                     sl_reply_error();
                     break;
                  };

                  if (!t_forward_nonack_udp("192.168.20.3", "5060")) {
                    xlog("L_ERR", "Forward to Presence Server failed\n");
                    sl_reply_error();
                  };

                  break;
              
            } else if (method=="NOTIFY") {
                route(8);
                break;
            };

            # -------------- Handle Aliases
            lookup("aliases");
            if (uri!=myself) {
                append_hf("P-hint: Alias External Destination\r\n");
                route(4);
                route(1);
                break;
            };

            # -------------- Handle case where user not registered
            if (!lookup("location")) {
                sl_send_reply("404", "User Not Found");
                break;
            };
        };

        append_hf("P-hint: USRLOC Applied\r\n");

        route(4);
        route(1);
    }

    route[1] {

        remove_hf("Proxy-Authorization");
        t_on_reply("1");

        if (!t_relay()) {

           if (method=="INVITE" || method=="ACK") {
             end_media_session();
           };

            sl_reply_error();
        };
    }

    route[2] {

        lookup("aliases");
        if (!isflagset(22)) {
         append_branch();
        };

        if (uri!=myself) {
         
          route(4);
          route(1);
          break;
        };

        # PSTN destined
        if (uri=~"^sip:9[0-9][0-9].*@") {
           strip(1);
           rewritehostport("192.168.20.4:5060");
           route(4);
           route(1);
           break;
        };

        if (!lookup("location")) {
                                                                                   
            if (does_uri_exist()) {
              rewritehostport("192.168.20.5:5060");
              route(4);
              route(1);
              break;
            } else {

              acc_db_request("404", "acc");
              sl_send_reply("404", "User Not Found");
              break;
            } ;

        };

        append_hf("P-hint: USRLOC Applied\r\n");
        #t_on_failure("2");
       
        route(4);
        route(1);
        break;
                                                                                   
    }


    route[3] {

    # -------------- REGISTER Handler

         if (!search("expires=0")) {
            append_hf("P-hint: Registration\r\n");
         };

        if (!search("^Contact:[ ]*\*") && client_nat_test("7")) {
          setflag(6);
          fix_nated_register();
          force_rport();
        };

        if (!is_from_local()) {
           acc_db_request("403 - Bad Domain", "acc");
           sl_send_reply("403", "Unknown Domain");
           break;
        };

        if (!www_authorize("", "subscriber")) {
           www_challenge("", "1");
           break;
        };

        consume_credentials();

        if (!check_to()) {
          acc_db_request("401 - Hijack Attempt", "acc");
          sl_send_reply("401", "Unauthorized");
          break;
        };


        append_time(); # Per RFC3261 Section 10.3 item 8


        if (!save("location")) {
            sl_reply_error();
            break;
        } else {

           t_replicate("192.168.20.3","5060");

        };


    }

    route[4] {

     
       if ((isflagset(6) || isflagset(7)) && !isflagset(8)) {
          setflag(8);
          use_media_proxy();
       };

    }


    route[5] {

    # -------------- INVITE/CANCEL Handler
    #

        if (client_nat_test("3")) {
              setflag(7);
              force_rport();
              fix_nated_contact();
        };

        lookup("aliases");

        if (uri!=myself) {
            append_hf("P-hint: Alias External Destination\r\n");
            route(4);
            route(1);
            break;
        };

        if (method=="INVITE" ) {

                if (!proxy_authorize("", "subscriber")) {
                    proxy_challenge("", "1");
                    break;
                };
                #consume_credentials();
            };


            # -------------- Forward to PSTN
            if (uri=~"^sip:9[0-9].*@") {
               strip(1);
               setflag(29);
               if (is_user_in("From", "prepaid")) {
                 rewritehostport("192.168.20.4:5060"); 
                 route(4);
                 route(1);
                 break;
               } else {
                 acc_db_request("401 - Subscriber not in prepaid group", "acc");
                 sl_send_reply("401", "Unauthorized");
                 break;
               };
            };
       

            # -------------- Forward to Voicemail (VM)
            if (uri=~"^sip:121@") {
              if (is_user_in("From", "voicemail")) {
                 avp_write("$from", "s:vmtarget");
                 avp_pushto("$ruri", "s:vmtarget");
                 prefix("99");
                 rewritehostport("192.168.20.5:5060"); 
                 avp_delete("s:vmtarget");
                 route(4);
                 route(1);
                 break;
              } else {
                  rewritehostport("192.168.20.5:5060"); 
                  rewriteuser("NoVmPriv");
                  route(4);
                  route(1);
                  break;
              };
            };

        # -------------- Check if DND enabled
        if (avp_db_load("$ruri/username", "s:donotdisturb")) {
          if (avp_check("s:donotdisturb", "eq/y/i")) {
              #------ If enabled, forward to Voicemail
              rewritehostport("192.168.20.5:5060"); 
              route(4);
              route(1);
              break;
          };
        };


        # -------------- Check if CFU enabled
        if (avp_db_load("$ruri/username", "s:callfwd")) {
          setflag(22);
        # DIVERSION
        add_diversion("call-forward-uncond");
          avp_pushto("$ruri", "s:callfwd");
          append_hf("P-hint: Unconditional Call Forward\r\n");
          route(2);
          break;

        };


        # -------------- If no user location found
        if (!lookup("location")) {
            if (method=="CANCEL") {
              route(1);
              break;
            };

            acc_db_request("404", "acc");
            sl_send_reply("404", "User Not Found");
            break;
        };


        if (method=="CANCEL") {
            route(1);
            break;
        };

        avp_write("$ruri", "i:99");

        if (avp_db_load("$ruri/username", "s:fwdnoanswer")) {

           # check that forwarded number is not the same as the dialed number
           if (!avp_check("s:fwdnoanswer", "eq/$ruri/i")) {
              setflag(27);
           };
        };

        avp_pushto("$ruri", "i:99");

        if (avp_db_load("$ruri/username", "s:callreturn")) {
           avp_db_delete("$ruri/username", "s:callreturn");
        };
        avp_write("$from", "s:callreturn");
        avp_db_store("$ruri/username", "s:callreturn");
        avp_delete("s:callreturn");

        t_on_failure("1");

        route(4);
        route(1);
    };
    }

    route[6] {

         revert_uri();
         if (is_user_in("To", "voicemail")) {  #
           rewritehost("192.168.20.5"); 
           append_branch();
           route(4);
           route(1);
         } else {
           rewritehostport("192.168.20.5:5060"); 
           rewriteuser("999");
           append_branch();
           route(4);
           route(1);
           break;

         };
          
    }

    route[7] {

        # -------------- Calls destined for PSTN
        rewritehost("192.168.20.4");    # <---- REPLACE IP W/ PSTN GW
        avp_write("i:45", "inv_timeout");
        t_on_failure("1");
        route(4);
        route(1);
    }

    route[8] {
     if ((src_ip==192.168.20.5) || (src_ip==192.168.20.3)){
      if lookup("location") {
       if (!t_relay()) {
         sl_reply_error();
         break;
       };
      } else {
       sl_send_reply("200", "OK");
       break;

      };
     };
    }


    route[9] {

       lookup("aliases");
       if (uri!=myself) {
           route(4);
           route(1);
           break;
       };

       lookup("location");

       route(4);
       route(1);
    }

    failure_route[1] {
       if (isflagset(26) && t_check_status("486") ) {
         add_diversion("user-busy");
         if (avp_pushto("$ruri", "s:callfwdbusy")) {
            append_hf("P-hint: Call Forward Busy\r\n");
            #append_branch();
            avp_delete("s:callfwdbusy");
            resetflag(26);
            route(2);
            break;
         };
       };

        if (isflagset(27) && t_check_status("408")) {
           add_diversion("no-response");
            if (avp_pushto("$ruri", "s:fwdnoanswer")) {
                append_hf("P-hint: Forward No Answer\r\n");
                avp_delete("s:fwdnoanswer");
                 rewritehost("192.168.20.1");   
                resetflag(27);
                route(2);
                break;
        };
        };

        if ( !isflagset(29) && (t_check_status("486") || t_check_status("408")) ) {
            route(6);
            break;
        };

        end_media_session();
    }

    onreply_route[1] {

            if ((isflagset(6) || isflagset(7)) && (status=~"(180)|(183)|2[0-9][0-9]")) {

                    if (!search("^Content-Length:[ ]*0")) {
                            append_hf("P-hint: NATed Reply\r\n");
                            use_media_proxy();
                    };
            };

            if (client_nat_test("1")) {
                    fix_nated_contact();
            };
    }

    ==============