OS X El Capitan: The Missing Manual

Broadband Connections

If your Mac is connected wirelessly or, um, wirefully to a cable modem, DSL, or office network, you’re one of the lucky ones. You have a high-speed broadband connection to the Internet that’s always available, always on. You never have to wait to dial.

Automatic Configuration

Most broadband connections require no setup whatsoever. Take a new Mac out of the box, plug in the Ethernet cable to your cable modem—or choose a wireless network from the menulet—and you can begin surfing the web instantly.

That’s because most cable modems, DSL boxes, and wireless base stations use DHCP. It stands for dynamic host configuration protocol, but what it means is “We’ll fill in your Network pane of System Preferences automatically.” (Including techie specs like IP address and DNS server addresses.)

Manual Configuration

If, for some reason, you’re not able to surf the web or check email the first time you try, it’s remotely possible that your broadband modem or your office network doesn’t offer DHCP. In that case, you may have to fiddle with the Network pane of System Preferences, preferably with a customer-support rep from your broadband company on the phone.

On the Network pane, click your Internet connection (Wi-Fi, built-in Ethernet, cellular modem, whatever). Click Advanced; click TCP/IP. Now you see something like Figure 15-3. Don’t be alarmed by the morass of numbers and periods—it’s ...