[...]
modparam("auth_db|permissions|uri_db|usrloc|acc|domain",
        "db_url", "postgres://openser:openser@localhost/openser")
modparam("auth_db", "calculate_ha1", 1)
modparam("auth_db", "password_column", "password")
modparam("nathelper", "rtpproxy_disable", 1)
modparam("nathelper", "natping_interval", 0)
modparam("mediaproxy","natping_interval", 30)
modparam("mediaproxy","mediaproxy_socket", "/var/run/mediaproxy.sock")
modparam("mediaproxy","sip_asymmetrics","/usr/local/etc/ser/sip-clients")
modparam("mediaproxy","rtp_asymmetrics","/usr/local/etc/ser/rtp-clients")
modparam("usrloc", "db_mode", 1)
modparam("registrar", "nat_flag", 6)
modparam("rr", "enable_full_lr", 1)
modparam("tm", "fr_inv_timer", 27)
modparam("tm", "fr_inv_timer_avp", "inv_timeout")
modparam("permissions", "db_mode", 1)
modparam("permissions", "trusted_table", "trusted")
modparam("avpops", "avp_url", "postgres://openser:openser@localhost/openser")
modparam("avpops", "avp_table", "usr_preferences")
modparam("acc", "log_level", 1)
modparam("acc", "log_flag", 1)
modparam("acc", "db_flag", 2)
modparam("acc", "db_missed_flag", 3)

route {

        # -----------------------------------------------------------------
        # Sanity Check Section
        # -----------------------------------------------------------------
        if (!mf_process_maxfwd_header("10")) {
                sl_send_reply("483", "Too Many Hops");
                return;
        };

        if (msg:len > max_len) {
                sl_send_reply("513", "Message Overflow");
                return;
        };

        # -----------------------------------------------------------------
        # Record Route Section
        # -----------------------------------------------------------------
        if (method=="INVITE" && client_nat_test("3")) {
                # INSERT YOUR IP ADDRESS HERE
                record_route_preset("<MY OPENSER PBULIC IP>:5060;nat=yes");
        } else if (method!="REGISTER") {
                record_route();
        };

        # -----------------------------------------------------------------
        # Call Tear Down Section
        # -----------------------------------------------------------------
        if (method=="BYE" || method=="CANCEL") {
                setflag(2);
                end_media_session();
        };

        # -----------------------------------------------------------------
        # Loose Route Section
        # -----------------------------------------------------------------
        if (loose_route()) {

                route(1);
                return;
        };

        # -----------------------------------------------------------------
        # Call Type Processing Section
        # -----------------------------------------------------------------

        setflag(3);

        if (!is_uri_host_local()) {
                if (is_from_local() || allow_trusted()) {
                        route(1);
                } else {
                        sl_send_reply("403", "Forbidden");
                };
                return;
        };

        if (method=="CANCEL") {
                route(1);
                return;
        } else if (method=="INVITE") {
                route(3);
                return;
        } else  if (method=="REGISTER") {
                route(2);
                return;
        };

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

        if (!lookup("location")) {
                sl_send_reply("404", "User Not Found");
                return;
        };

        route(1);
}

route[1] {

        # -----------------------------------------------------------------
        # Default Message Handler
        # -----------------------------------------------------------------

        t_on_reply("1");

        setflag(2);

        if (!isflagset(8)) {
                setflag(8);
                log(1,"Uso Media Proxy");
                use_media_proxy();
        };

        if (!t_relay()) {

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

                sl_reply_error();
        };
}

route[2] {

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

        sl_send_reply("100", "Trying");

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

        if (!www_authorize("","subscriber")) {
                www_challenge("","0");
                return;
        };

        if (!check_to()) {
                sl_send_reply("401", "Unauthorized");
                return;
        };

        consume_credentials();

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

route[3] {

        # -----------------------------------------------------------------
        # INVITE Message Handler
        # -----------------------------------------------------------------

        if (!allow_trusted()) {

                if (!proxy_authorize("","subscriber")) {
                        proxy_challenge("","0");
                        return;
                } else if (!check_from()) {
                        sl_send_reply("403", "Use From=ID");
                        return;
                };

                consume_credentials();
        };

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

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

        if (avp_db_load("$ruri/username", "s:callfwd")) {
                setflag(22);
                avp_pushto("$ruri", "s:callfwd");
                route(6);
                return;
        };

        if (!lookup("location")) {

                sl_send_reply("404", "User Not Found");
                return;
        };

        if (avp_db_load("$ruri/username", "s:fwdbusy")) {
                if (!avp_check("s:fwdbusy", "eq/$ruri/i")) {
                        setflag(26);
                };
        };

        if (avp_db_load("$ruri/username", "s:fwdnoanswer")) {
                if (!avp_check("s:fwdnoanswer", "eq/$ruri/i")) {
                        setflag(27);
                };
        };

        t_on_failure("1");

        route(1);
}

route[6] {

        # --------------------------------------------------------------------
        # Call Forwarding Reply Route Handler
        #
        # This must be done as a route block because sl_send_reply() cannot be
        # called from the failure_route block
        # --------------------------------------------------------------------

        lookup("aliases");

        if (!isflagset(22)) {
                append_branch();
        };

        if (uri!=myself) {

                route(1);
                return;
        };

        if (!lookup("location")) {

                sl_send_reply("404", "User Not Found");
        };

        route(1);
}

onreply_route[1] {

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

                if (!search("^Content-Length:[ ]*0")) {
                        use_media_proxy();
                };
        };

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

failure_route[1] {

        if (t_check_status("487")) {
                return;
        };

        if (isflagset(26) && t_check_status("486")) {
                if (avp_pushto("$ruri", "s:fwdbusy")) {
                        avp_delete("s:fwdbusy");
                        resetflag(26);
                        route(6);
                        return;
                };
        };

        if (isflagset(27) && t_check_status("408")) {
                if (avp_pushto("$ruri", "s:fwdnoanswer")) {
                        avp_delete("s:fwdnoanswer");
                        resetflag(27);
                        route(6);
                        return;
                };
        };

        end_media_session();
}