添加映射：
netsh interface portproxy add v4tov4 listenport=9888 connectaddress=192.168.20.5 connectport=9888
删除映射：
netsh interface portproxy delete v4tov4 listenport=9888
windows server配置vpn
windows 端口映射
原文：http://www.cnblogs.com/IWings/p/7462881.html
