Extend fungrer kun med Express, Extreme eller Express som hovedbase, dvs kun Apple devicer, Med ethernetkabel kan den utvides også andre,
Apple seems to be saying in a round-a-bout way here that other routers are not supported for wireless range extensions (with a router connected to Ethernet and the Express not):
Extend an existing Wi-Fi network’s range.
If you already have a wireless network in your home and want to extend its range, AirPort Express can help. Just place it in range of your primary base station — an AirPort Extreme, Time Capsule, or another AirPort Express — and near the area where you want your wireless connection. Launch the easy-to-use AirPort Utility app on your iOS device or Mac, and you’re mere minutes away from long-range Wi-Fi enjoyment.
However, this is only if your AirPort Express is not connected to Ethernet. Otherwise, you can setup a roaming network. The newer Airport Express models (the ones compatible with 802.11n) can do this.
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