Archived - Mac OS: How to Get an IP Address for Connecting to the Internet
Internet connection requires an IP address. This document describes how to get an IP address.
An IP address defines your computer's location on the Internet, similar to the way that a street address and postal code identify your home. Without an IP address, you cannot connect to the Internet. How you get your IP address depends on what type of network or Internet service provider you have. From the sections below, choose the type that matches your network or Internet service provider.
Computers on institutional networks most likely already have a valid TCP/IP configuration, often indicated by the ability to connect to the Internet. If not, consult your network administrator before proceeding. If your network administrator does not have Mac OS X-specific instructions, technical document 106715 will explain what questions you need to ask and how to set up your connection ("Mac OS X: How to Connect to the Internet via Cable, DSL, or Local Area Network (LAN)").
Single computer connected to the Internet
Your Internet service provider must give you a valid TCP/IP configuration to connect your computer to the Internet. Follow instructions provided by your Internet service provider. If your Internet service provider does not have Mac OS X-specific instructions, you can learn what questions to ask and how to set up your connection from "Mac OS X: Internet and Network Topics (Getting Connected, Troubleshooting)".
Isolated private network
This is two or more connected computers that do not have a connection to the Internet. You need to assign a TCP/IP address and subnet mask to each computer. For Mac OS X, these are set in the Network pane of System Preferences. For Mac OS 9 computers, the settings are in the TCP/IP control panel. You can achieve this two ways: manually, or via DHCP.
- To use the DHCP method: Choose Using DHCP from the Configure pop-up menu on both computers. Since you do not have a DHCP server on this simple network, this will cause each computer to automatically assign itself a TCP/IP address that begins with 169.
Note: Though addresses in private ranges (such as 169.x.x.x) are usually not routed for traffic on the public Internet, they may in rare cases be routed within private networks. Your Internet service provider or institutional network, for example, could choose to assign addresses in these ranges.
- The manual method: Choose Manually from the Configure pop-up menu on each computer. The TCP/IP address must be different for each computer. Choose addresses in the range 10.0.0.1 to 10.0.0.255. The subnet mask on each computer should be 255.255.255.0. For more information on private network addressing, see technical document: "TCP/IP: Setting Up a Private Network"
Private network connected to Internet
This is two or more connected computers that also share a single IP address for connecting to the Internet, a technique known as "IP Masquerading" or Network Address Translation (NAT). This common solution is used when your Internet service provider only allows one IP address and/or DHCP lease for your account. A router holds the "public" IP address from your Internet service provider, while the other computers have "private" addresses. Steps not covered by this document are required, including router setup. See the documentation included with the router you intend to use. The Apple AirPort Base Station is capable of performing this routing function.
Note: This note applies to all network types. Mac OS X versions 10.0 to 10.0.4 can only connect to AppleShare over TCP/IP. For information related to the TCP/IP requirement, see technical document: "Mac OS X 10.0: Connecting to AppleShare or File Sharing Requires TCP/IP".