Apple iMac (Early 2006) - Manual (Page 106)

106 Appendix C Connecting to the Internet
Network Connections
Make sure the Ethernet cable is plugged into your computer and into the network.
Check the cables and power supplies to your Ethernet hubs and routers.
If you have two or more computers attempting to share an Internet connection, be
sure that your network is set up properly. You need to know if your ISP provides only
one IP address or if it provides multiple IP addresses, one for each computer.
If only one IP address is used, then you must have a router capable of sharing the
connection, also known as network address translation (NAT) or “IP masquerading.”
For setup information, check the documentation provided with your router or ask the
person who set up your network. You can use an AirPort Extreme Base Station to share
one IP address among multiple computers. For information about using the AirPort
Extreme Base Station, check Mac Help or visit the Apple AirPort website at
www.apple.com/airport.
If you cannot resolve the issue using these steps, you should contact your ISP or
network administrator.