基本的NAT实现的功能很简单，在子网内使用一个保留的IP子网段，这些IP对外是不可见的。子网内只有少数一些IP地址可以对应到真正全球唯一的IP地址。如果这些节点需要访问外部网络，那么基本NAT就负责将这个节点的子网内IP转化为一个全球唯一的IP然后发送出去。(基本的NAT会改变IP包中的原IP地址，但是不会改变IP包中的端口)-achieve basic NAT function is very simple. Subnets within a reservation to use the IP subnet, These external IP is not visible. Subnet only a small number of IP addresses corresponding to be the only truly global IP addresses. If these nodes need access to external networks, NAT on such a basic responsibility to the children of this node within the IP network into a single global IP then sent out. (Basic NAT will change the IP packet original IP address, but would not change the IP packet ports)