Q: Setting up an Airport Express as extender over lan

Hi there

I've recently bought several Airport Expresses so I can use AirPlay on several stereos throughout my house. Of course this didn't work with a third-party router, so I installed an Airport Express (nr 1) as a base station with the cable from the router as input (into the WAN port). Out of the LAN port comes a cable to a switch.

Now, in the places where I have a stereo, I put another Airport Express (nr 2). To fortify our wifi-signal I want to have it extend the regular network. Logically, I choose the 'Wireless mode' as 'Extend a wireless network'.

Since there is a LAN port near the 2nd Airport Express, it is logical to plug it into the 2nd Airport Express. Should be as simple as that to set up, amiright? NO! I'm not right! Plugging in the ethernet cable drops the network. You can't connect anymore to the networ. However, pulling the LAN out again seems to fix it again. What am I doing wrong here? I thought setting this up would be easy, but heck I've wasted hours trying to figure this out. How hard can it be to name Airport Utility (for Windows in my case) different from Airport utility for iOS. The latter has much less functionality.

Do I have a flaw in my setup, or am I doing something wrong in the setup? With previous routes this setup worked just fine.

Thanks