What do the colored dots next to my network connections mean?

In the Network pane of System Preferences you’ll see a colored dot next to each network interface. A green dot means that the network interface is configured and working correctly, a red dot means that the interface is not active, and a yellow dot means that the interface is active, but might not be able to connect to the Internet.

Your Mac will automatically use the best network connection

If you use your Mac in an environment where you’re connected to a network through an Ethernet and AirPort connection your Mac will automatically use the interface that gives the best performance. In most cases this will be the Ethernet connection, but if an administrator is doing maintenance on a router on that network, your Mac will automatically switch to the AirPort network, and in most cases you won’t even notice what has happened.

Use the FireWire port as a network interface

In addition to using the modem, Ethernet or AirPort interface on your Mac to connect to a network, you can also use a FireWire port. Using the FireWire port on your computer is a great way to quickly connect two computers and to transfer files between them if no other network is available.

Understanding network locations

A network location is needed whenever you have two or more different configurations for the same network interface. For example, if you use your Ethernet port to connect to a network at work and at home, and work uses a DHCP server and you have a fixed IP address at home, two locations will be used to switch between the two networks.