Extended wireless network - how do I know which Airport I'm on?

[ss957916]

I have a Time Capsule as my main wifi router and have extended it to my upstairs using an Express.

How can I tell which airport my MBP is actually connected to??

 

[JediMeister]

Do you have 10.6? Hold down on the option key, and click on the AirPort icon. Under the physical mode should be listed the BSSID which is the MAC address of the router you're connected to. You get something similar with 10.5 except it doesn't list the type of network (a, b, g, or n) and the BSSID is not labeled as such. Compare the address listed there with the one on the router(s) and you can see which you are connected to.