Nat and transparent proxy are very important function modules of firewall . nat would do network address translation for outbound packet so that inside hosts can use reserved ip addresses and outside hosts can not visit inside ones directly to realize one - way communication Nat和透明代理是其中非常重要的功能模块。 nat对内网主机的出网数据包进行网络地址变换，内网主机可以使用保留地址上网，外网主机无法直接访问内网主机，从而实现单向通信。
