Can you set up an Airport Express to create a wired network as part of a larger network that the Express is connected to wirelessly? Yes, you can.

I had a hard time tracking down this info so I thought I’d post it here for the benefit of others.

I recently added a Sony Blu-Ray player to my basement home theater system. I’m really pleased with the device; besides playing Blu-Ray discs quite nicely, it also supports streaming video from Netflix and Amazon. I had considered getting a second Roku, but this is fitting the bill nicely. The only problem I had was getting it connected to the network as it doesn’t have built-in wifi.

I had a similar problem with the PowerMac G5 I moved to the upstairs office which similarly doesn’t have wifi. Basically, I needed a way to get working wired connections to the upstairs and basement of my house. I knew this was theoretically possible with the hardware I already had (Airport Extreme base station and 2 Airport Express units), but I couldn’t find an overview of how to properly set it up.

So the first question is: fundamentally, can this work? The answer is yes.

Depending on how you have it set up, the Ethernet port can function as a LAN port (defined as either simple bridging or sharing your Internet connection via network address translation)… When it is set up as a WDS remote station, it can act as a LAN port.

I first tried to get an Express to extend the wireless network created by my DLink router. This will not work. While the Express will connect to a 3rd party wireless network for Airtunes, it will not extend a 3rd party network. In short, you can’t do what I want to do with a non-Apple wireless router.

In client mode AirPort Express does not offer itself as a wireless access point or use its Ethernet port.

In order to get the Express’ ethernet port live in extending the network, you must have it set up as a relay/remote on a WDS network.

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.

A couple of tips for setting up the WDS configuration:

1. You will need to copy/paste the Airport ID of each airport into the proper location in the admin panels. You need to enter the Airport ID of the relays/remotes into the Main and the address of the Main into the remotes.
2. You must make sure that the wireless network settings of the WDS relays/remotes match that of the WDS main. This means the network name, authentication settings, and the channel.

Once you have configured the Extreme as the WDS Main and the Expresses as WDS relays/remotes, the ethernet ports on the Expresses will also extend the network, just as desired. Works like a champ!

If you need to connect more than one wired device from the location of an Express, you can do so by adding a hub. Connect the uplink port on the hub to the Express, and the rest of the ports on the hub will now all extend the network.

Hopefully this will help someone with similar questions.