Setting Up a Relay Station with AirPort Express

Setting up an AirPort base station (ABS) is something Apple customers do every day. However, adding an AirPort Express (AE) as a relay, to extend the range of a local Wi-Fi network, is a bit trickier and is not extremely well documented. Here’s how to do it.

There are lots of ways to set up a local wireless network and even more ways to go wrong trying to set up complex configurations. This HOWTO is very specific: it deals only with configuring an AirPort Extreme base station in partnership with an Airport Express in order to extend the range of your wireless network. This is helpful in a situation where you might want to work outside at your home, on a patio, but that location has too weak a signal from your AirPort base station. Basically, what Apple calls a “Relay” station can be created, and the applicable Knowledge Base article is HT2044. It’s a little out of date.

Apple diagram

Apple’s diagram from KB HT2044. Credit: Apple, Inc.

Note Apple’s explanation: “A remote base station connects wirelessly to the main station and extends (or “rebroadcasts”) the wireless network to clients that are not in range of the main. A relay base station is like a remote, but it has the additional function of extending the wireless network to a remote which isn’t within range of the main. There can be only one relay between a remote and a main.

In this scenario, we create a relay, which is more flexible down the road, and still has the function of extending the range of the wireless network.

Both the base station and the relay station need to be (re)configured with the AirPort found in /Applications/Utilities.

The first step, if you alterate between a wired and a Wi-Fi connection at home through your current AirPort Extreme is to get on the wireless, AirPort network with the Mac you want to use for this project. A notebook is preferable if you have one.

The next step, probably the safest bet, is to reset your AirPort Express. There’s a small button on the back, just big enough for a small paperclip or tiny jeweler’s Phillips screwdriver. Plug it in near your base station — in such a way that you have access to that reset button and can also monitor the LED light on top. Push the paper clip and hold for a few seconds until you see the yellow light start to flash rapidly, then let go. This will reset your AirPort Express to its factory settings. It will still transmit, and you should see its default configuration in the AirPort, like this:

Default AE

Default AirPort Express

The default AE is at the top in the diagram above. Note that an AirPort Express in its default configuration has the name “Base Station” + “last six digits of MAC address.” Write down the full MAC address, that is all six pairs of numbers.

Configuring the Base Station

Before we configure the AE, however, some changes need to be made to the AirPort base station to support what’s called a Wireless Distribution System (WDS) network.

A practice of mine is to have a directory at the root level of my admin user account called “System Support”. At this time, you should use the Airport Utility to document the current settings of your base station in case something goes awry. Select the base station from the list, click on “Manual Setup” and note the tabs across the top: Summary, Base Station, Wireless, etc. Select each of those tabs and take a screen shot. (CMD+SHFT+4) Place these (renamed) screen shots in your System Support directory. Now you’re ready to make some changes to the base station.

1. In the “Wireless” tab note the popup at the top. Change it to “Participate in a WDS network.” A new tab will now appear: “WDS.”

2. Select: “Allow this network to be extended.” Now, write these items down, which should already be set: Wireless Network Name, Radio Mode, Channel, Wireless Security (should be WPA2 Personal. If not fix it).

3. Click the WDS tab.

4. Make sure the popup at the top is set to “WDS Main”.

5. Select “Allow wireless clients”.

6. Click the “+” symbol under the window and enter the Mac Address the “AirPort ID” of the AE that you wrote down above. Give it a description and click “OK.”

Your AirPort Base station is now ready to connect to a relay AE. Click “Update” at the bottom of the window. The ABS will reboot, and you’ll be off the air for a few seconds. When it comes back up, you’ll (hopefully) see a solid green light, you’ll have wireless access as before, and the ABS will be ready to connect to the AE relay. (If you see a “WDS error” and a yellow light for the ABS in the Airport Utility , click on the yellow light, then select “ignore”. The light will return to green. When the AE comes on line, all will be well.)

Write down the MAC address of the ABS.

Configuring the AirPort Express

Because you reset the AE, you’ll have to go through the base Station, Wireless, and WDS tabs, entering new data.

1. Under Base Station, select a name for the AE and a good admin password. Having it stored in the keychain makes things easier. Use the Apple time standard if you wish.

Base Station settings

Base Station Settings

2. Under Wireless, select the popup “Participate in a WDS network.” Give the network the SAME name, Radio Mode, Channel and security that you wrote down above. Leave the Wireless Options at their defaults.

Wireless Settings

Wireless Settings

3. Under WDS, the “Allow wireless client” is selected if you intend to add a remote later. In this case, it doesn’t matter. In the WDS Main field enter the MAC address of the ABS. The WDS remotes field is used only if you add a remote AE later, which is beyond the scope of this article.

WDS Setings

WDS Settings

4. Click the Update button to reboot the AE. If it doesn’t come up with a solid green light, you’ve made a mistake. The most common one is giving the AE a different Wireless Network Name than the ABS. If you can’t see it in the AirPort Utility after it reboots, even if you switch to the renamed second network, you’ll have to reset it and start over.

Once everything is working, take a second set of screen shots, ABS and AE, and label them carefully for future reference. Now you can unplug the AE and move it to another location, so long as it’s still in range of the base station.

Selecting the Network

You may be wondering, if the ABS and the AE have the same network name, how do you select the desired one in the AirPort menu bar? The answer is, you don’t. The wireless client (MacBook, iPad, iPhone) selects the one with the greater signal strength. Here’s what iStumbler shows in my office for my network “marty-n” (The AE’s MAC address ends in “FF” and the ABS MAC address ends in “47”. The rest belong to neighbors, and I’ve suppressed these MAC addresses for privacy.

As you can see, the ABS is a lot stronger when I’m in my office with a MacBook, but the reverse is true for the AE in an upstairs bedroom.

Office iStumbler

iStmbler in Office

Bedroom iStumbler

iStumbler in Bedroom 


This is a detailed process, and lots of things can go wrong. At one point, in my own configuration, I had blinking yellow lights on both the ABS and the AE, thanks to small mistakes. (For example, I replaced an ABS “Snow” with the “Flat” version, but forgot to make the WDS changes.) That’s why taking those screen shots when you have a good configuration is so important. Especially if you, someday, replace a failed unit and need to start from scratch.

This is harder than it has to be, and I’ve heard about a Wizard that can step one through all this. But I’d rather know exactly what’s going on. Unfortunately, the process is tedious and not well documented by Apple for the latest version of AirPort Utility and products.

Good night, and good luck!