Is there a way you can determine what wifi device you are actually connected too?
Sure.
Open AirPort Utility and click on the AirPort Extreme and a smaller window will open with information about the AirPort Extreme. Look for Wireless Clients to see which particular Wi-Fi devices are connecting to the AirPort Extreme at the time.
Do the same for the AirPort Express that is providing a Wi-Fi signal to see which Wi-Fi devices are connecting to the AirPort Express.
Wireless Clients are displayed with either the device name, the IP Address, or the MAC Address of the device. With luck, most devices will use the device name.
Is there a way to force a wifi connection on my laptop (or other devices) to my AP Express through say an ip address or a MAC address??
Unfortunately, no. In general....and in theory.....Wi-Fi devices will connect to the AirPort with the strongest signal......but this is not always the case......since the theory does not always work all that well in the real world.
If you want a Wi-Fi device to connect to a given AirPort, temporarily turn off the Wi-Fi on the Wi-Fi device, move it close the AirPort to which you want it to connect, then turn the Wi-Fi back on at the device. In theory, the Wi-Fi device will connect to the strongest signal from the closest AirPort.
For example, if you had an iPhone, you could tap Settings, then tap WiFi and switch the iPhone to AirPlane Mode to temporarily turn off the Wi-Fi. Then, move the iPhone close to the AirPort and switch AirPlane Mode off, so the iPhone will connect using Wi-Fi.
If you have a Mac, click on the Wi-Fi menu at the top of the screen and turn off the Wi-Fi. Then move the Mac near the AirPort to which you want it to connect, and turn the Wi-Fi back on at the Mac.
From what I am able to see and verify on my current AP Express, it does NOT appear I am using the Express for wifi, but have a connection to my AT&T Hotspot.
That's correct. The Express that is connected to the AT&T hotspot is "joining" the Wi-Fi network that the hotspot provides. The Express does not produce a Wi-Fi network signal when it "joins" a network, but the Ethernet port(s) on the Express are enabled, so you can connect an Ethernet device to the Express.
You are using the Express that connects to the hotspot in a very special way that is not often used. Apple provides virtually no documentation on this special type of application. To review, we have not recommended this type of setup, but it is the only way that you will be able to use the AT&T hotspot and an AirPort Extreme given the circumstances.
Other AirPorts will be able to connect to the AirPort Extreme if you need to "extend" the network provided by the AirPort Extreme.
