Manually Choose an IP Address Range for Your MacBook Network

By Mark L. Chambers from MacBook All-in-One For Dummies, 2nd Edition

If you need to manually assign IP addresses when networking your MacBook, you need to manually configure the Transmission Control Protocol/Internet Protocol (TCP/IP) Properties. Keep in mind that for now, you’re not concerned with the Internet — just computers on the local network.

A result of being on a local network — because it’s not connected to the Internet, it’s also called a private network — is that you must use IP addresses that are reserved for private network use. You can use a few different ranges of IP addresses, but choose an address range from the 192.168.x.x (or 10.0.x.x) networks.

Use IP addresses where the first two octets are 192 and 168 (192.168) or 10 and 0 for AirPort Extreme (10.0).

Octet numbers are conjoined by periods.
For the third octet, select any number between 1 and 254.

It doesn’t matter which one you choose as long as you use this same third number on all computers on your network.
For the fourth octet, select any number between 1 and 254.

Make sure that every computer on your local network has a different fourth octet number. This is very important; otherwise, your network doesn’t work.
Use 255.255.255.0 as your subnet mask.

For instance, suppose that you’re using three computers on your network. All the IP addresses that you use will start with 192.168. Next, suppose you choose 123 for the third octet. (Remember that you can choose any number between 1 and 254.)

Finally, for the fourth octet, choose the numbers 100, 105, and 110 for the three computers, respectively. (Again, you can choose any numbers between 1 and 254.) The resulting IP addresses used on the three computers are

192.168.123.100

192.168.123.105

192.168.123.110

After you know the IP addresses and the subnet mask that you’re going to use, start setting up each computer.

Select any of your Macs to start with and open System Preferences (either from the Apple menu or from the Dock).
From the System Preferences dialog, choose Network.

The Network pane appears.
Click Ethernet in the list.
Click the Configure IPv4 pop-up menu and choose Manually.
Enter the IP address for this machine (192.168.123.105 in this example) in the IP Address text box.
Enter the subnet mask of 255.255.255.0 in the Subnet Mask text box.
If you’re using a router or hardware Internet sharing device, enter the IP address used by the router in the Router text box.
Click the Apply button, and your new network settings take effect.
Press Command+Q to quit System Preferences.

Repeat this same procedure with the other IP addresses for each of the other Macs that are connected to your network.

Most ISPs also supply DNS server addresses and search domains. If your ISP included DNS server addresses or search domains, don’t forget to type them into the corresponding boxes on the TCP/IP panel.