Network Address Translation (IP Masquerading)

Network Address Translation (NAT) permits sharing a single IP address (for example, from a PPP or broadband connection) with an entire internal network. NAT is very popular with home and small office networks. IPv4 addresses are in short supply, and furthermore, ISPs do not really want to bother with more routing than they can handle. As mentioned in Routers, many small routers support NAT. In Linux, the variant of NAT that most people use is known as IP masquerading.

The basic idea behind NAT is that the machine with the Internet connection acts as a proxy between the internal network and the rest of the Internet. Consider a network like the one back in Figure 5-1 on page 94, and assume that the router ...

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