Next Previous Contents 4. Each number is between zero and 255. Interfaces in the same network tend to have neighboring IP addresses. Remember also that a router is a node with interfaces on more than one network, so the router will have one IP address for each interface.
Routes can either point to a link, or a particular node which is connected to another network.
For example, when you dial up to the ISP, your default route will point to the modem link, because that's where the entire world is. But if you have a permanent machine on your network which connects to the outside world, it's a bit more complicated. In the diagram below, my machine can talk directly to Tridge and Paul's machines, and to the firewall, but it needs to know that packets heading the rest of the world need to go to the firewall, which will pass them on. Just like a phone number can be broken up into an area prefix and the rest, we can divide an IP address into a network prefix and the rest. To make things confusing, there is another way of writing netmasks.