Linux Shell Scripting Cookbook - Third Edition

How it works

There are three sets of IP addresses set aside for non-routing use. That means that no network interface visible to the Internet can use them. They are only used by machines on a local, internal network. The addresses are 10.x.x.x, 192.168.x.x, and 172.16.x.x-> 172.32.x.x. In this recipe, we use a portion of the 10.x.x.x address space for our internal network.

By default, Linux systems will accept or generate packets, but will not echo them. This is controlled by the value in/proc/sys/net/ipv4/ip_forward.

Echoing a 1 to that location tells the Linux kernel to forward any packet it doesn't recognize. This allows the wireless devices on the 10.99.66.x subnet to use 10.99.66.55 as their gateway. They will send a packet destined ...