How do I use Back to My Mac (to time capsule) in a multiple Airport configuration?

Question

I have an Airport Extreme with an attached USB drive that I've been accessing via Back to My Mac using these instructions (see the section with the text, "...access files on a hard drive connected to an AirPort Extreme...").

Recently I extended (over Ethernet) my Airport network using an Airport Express upstairs. i.e.

Airport Extreme with USB drive (downstairs) <--Ethernet--> Airport Express (upstairs)

I used these instructions (see the first post by Bob Timmons) to extend my network. I can tell that the network extension is over Ethernet because AirPort Utility shows both Airports connected to each other with a solid line (extension over WiFi uses a dashed line).

However, this makes my downstairs Airport Extreme disappear from Back to My Mac. Using Bonjour Browser on a remote Mac, I can see only the upstairs Airport Express:

#######.members.btmm.icloud.com - 4
  Airport Base Station (_airport._tcp.) - 1
    airport_upstairs
  Apple File Sharing (_afpovertcp.tcp.) - 2
    home_mac_1
    home_mac_2

Notice that only airport_upstairs is visible via Back to My Mac (even though airport_downstairs is the one configured for Back to My Mac). Has anyone else run into this problem--do you know how to fix it?

Answer 1

It turns out that only one Airport at a time is visible via Back to My Mac. I had Back to My Mac configured on both airport_downstairs and airport_upstairs. As soon as I disabled Back to My Mac on airport_upstairs and restarted both routers, airport_downstairs appeared in Back to My Mac.

I suspect that the last Airport to start up is the one that appears on Back to My Mac, though I haven't verified this.