Along the left side of the Network window, you'll see any network avenues available to you. Exactly what you see here depends on the Mac you're using. A Mac that sports an ethernet port and carries Wi-Fi circuitry will, at the very least, display ethernet and Wi-Fi entries. A green dot next to any entry indicates that the connection is active and available to use. A yellow dot means that the connection could be active, but it's not yet configured. And a red dot tells you that there is no connection (a FireWire entry will show the red dot if there's no FireWire cable attached to your Mac, and the Wi-Fi item will have its own red dot if you've turned Wi-Fi off). You may also see listings for Thunderbolt Ethernet, USB Ethernet, FireWire, Thunderbolt FireWire, and Bluetooth PAN. We'll concern ourselves with ethernet and Wi-Fi, as they're the most commonly used connections.
Select one of these active connections (again, one with a green dot). If you've selected Wi-Fi, you'll see a Status entry to the right, which should read Connected. To its right is a Turn Wi-Fi Off button. To disable Wi-Fi, just click this button. Below the button you'll see the name of the network you're connected to as well as the IP address assigned to your Mac.
If you choose an active ethernet connection, you'll spy the same Connected entry with an IP address below. (Note that if you have both an ethernet and a Wi-Fi connection active, this IP address will be different than the Wi-Fi address because each connection gets its own internal IP address). In most cases, you should then see Using DHCP in the Configure IPv4 pop-up menu, along with your Mac's IP address, subnet mask, router, DNS server, and search-domain information. You can ignore the bulk of this information.
Troubleshooting your network
There are, however, two items I want to draw your attention to. The first is the Advanced button. Click it and a sheet appears that is sure to set the new Mac user's teeth on edge (so many numbers and acronyms!). Don't panic--we're going to look at one entry only.
If you find that you're unable to make an Internet connection and that the dot next to your normally active connection has turned yellow, it may be because your Mac has become confused about its IP address. In such cases it can help to renew that address. To do this, in the Advanced sheet, click the TCP/IP tab and click the Renew DHCP Lease button. This sends your router a "We need to reestablish our normally cozy relationship--could you make sure we're on the same page?" message. With a little luck, renewing that lease will restore your connection. When you're finished, click OK.
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