I recently noticed that Time Machine on both my Macs (Mountain Lion, 10.8.3) seem to think that my Airport Extreme base station (AEBS) + USB hard drive is actually a Time Capsule. Screenshots below. BTW, I asked this question on the official support status of AEBS + USB HDD, but this question is different (though related)
Question: Why does Time Machine (on Mountain Lion) think that an AEBS with an external HFS+ USB drive is a Time Capsule? I don't recall doing anything special but are there some special settings that "make it so"?
TM thinks it's backing to a Time Capsule
TM performing a backup to the USB HDD (HFS+) attached to the AEBS