https://github.com/rosedu/OpenSIPS/blob/master/examples/nathelper.cfg

http://opensips-open-sip-server.1449251.n2.nabble.com/Opensips-Nat-RTPProxy-in-bridged-mode-td7588578.html

http://www.lac.inf.puc-rio.br/moca/msipua/opensips_NAT.cfg

http://git.sip-router.org/cgi-bin/gitweb.cgi?p=sip-router;a=blob;f=examples/kamailio/nathelper.cfg;h=56c0caec4d2f1402ad8fa642bbd6d5df74c1ec71;hb=HEAD

http://www.cnblogs.com/languoliang/archive/2013/04/18/opensips-cfg.html

http://pastebin.com/87J1TSGz