Rules for IP Addressing when Upgrading to Lion Server

By John Rizzo

If you’re upgrading Snow Leopard or Lion client to Lion Server, you will need to set the IP address before starting the installation. When you set an IP address manually (known as static addressing), you need to follow some rules. An IP address takes the form of four numbers from 0 through 255, separated by periods, such as 169.254.13.3.

The total IP address range is 000.000.000.000 through 255.255.255.255, but within that, there are some ranges that are used for specific purposes, such as public and private IP addresses.

A public IP address is one that the entire Internet can see. Every computer on the planet that the Internet can directly see has a unique public IP address. Usually, your Internet service provider provides a public IP address, either manually or automatically.

A private IP address is one that the Internet can’t see because the computer is connected to the Internet through an Internet gateway or router. The Internet sees only the IP address of the gateway.

The computers on this type of local network use private IP addresses from one of several private address ranges. You might give your server a private IP address if another server or hardware box is acting as the Internet gateway. (You can also have a private IP address assigned automatically through DHCP.)

There are several private address ranges. One is the range that starts with 169.254: 169.254.0.0169.254.254.255. Note: For this range, the last number can be 255, but the one before it can only go as high as 254. The other two private ranges are 10.0.0.1 through 10.255.255.254 and 192.168.0.1 through 192.168.0.254.

If you manually configure the IP addresses of your Mac for a local network, you can use IP addresses from any of these ranges as long as all the Macs on the network are in the same range.

They also need the same subnet mask, and no two computers on your local network, or subnet, can have the same IP address. A subnet consists of all the computers connected to one Ethernet port on the server.