Tutorial: Turn Your Mac Into an AirPort Base Station

AirPort SymbolYou may not know this, but if you have more than one Mac and you’d like to share your Internet connection between them, there’s no need to buy an AirPort base station. Mac OS X comes with the software you need to turn almost any Mac into a base station all by itself.

So, if you have, say, an iMac in your home office and two MacBooks floating around your home, you can share a single cable modem connection between all three computers without purchasing any more equipment.

The idea is pretty simple: the first thing you need to do is get one Mac connected to the Internet. The good news is that, if you have a working Internet connection, Mac OS X is smart enough to do that for you; just plug an Ethernet cable between your broadband modem and your Mac. That is the only wired connection you’re going to need to make.

The second step is to set that Mac up to share its Internet connection with others, and to configure all of the related preferences. Finally, you connect your mobile machines to the network you created in step two, and you’re done.

Setup Diagram

The only requirements are that the “base station Mac” has to have both an Ethernet port (they all do) and an AirPort card (all of the current notebooks, iMacs and Mac minis do, it’s an option on the Mac Pro). Also, you need to be running Mac OS X. I am not sure which versions are required, but I know both Tiger and Panther can do this. (If anyone tries with a version earlier than Panther, please let us know in the comments how it goes.)

This works best if your Base Station Mac is a desktop machine because it’s got to be up and running whenever the other machines want to connect to the Internet. So if you use a notebook, your network will go down whenever you put it to sleep or shut it down.

On your Base Station Mac, open System Preferences and choose the Sharing Pane. This is where you go to turn on things like Printer Sharing and File Sharing… and it’s also where you’ll find the setup options for Internet Sharing, the magic mojo that will make your network run.

Once the Sharing Pane opens, click on the Internet tab at the right end of the bar to bring up the relevant options. Now, this screen is so simple that most of this explanation is totally unnecessary. Nevertheless, here it is: before the big Start button becomes clickable, you’re going to need to choose which “port” you want to use to share your internet connection.

Keep it simple and check AirPort. All that means is that, when the Internet comes in to your Base Station Mac’s Ethernet port, you’re going to share it out of the AirPort port. The AirPort Options button is where you give your network a name and set up its password. Do this, then click the big, ol’ Start button. Once you’ve done that, you’re home free.

Now look up at your Menu Bar where your AirPort icon usually sits… it’s different! The icon now shows that you’re running an outbound network and all your other Macs should see it automatically. Just turn on one of the machines that you want connected to your new network and hit the AirPort Menu. Type in the appropriate password, and off you go. Simple, no?

Except for the fact that your Base Station Mac needs to be on all the time, there is no real downside to this technique. Your ISP may limit how many computers you can connect to a single modem but, barring problems with that, you should have no trouble at all. Experienced readers may want to check out the Printer Sharing settings in the Services section of the Sharing Pane to setup a single USB printer on your Base Station Mac, which can be accessed from all your wireless machines.

Let us know in the comments how it goes!