Use an ingress filter on your network to ensure that no packets enter your outside boundary with a source address of your internal network. 在网络中使用入口过滤器来确保没有使用你的内部网络的源地址的包进入你的外界。
A firewall inspects the source and destination address of each message that crosses its path. 防火墙检查经过它的每一条消息的源地址和目的地址。