wpa_supplicant, hostap & virtual access points?

[Tony Espy]

I recently caught wind of something called 'Virtual Access Points' which 
allows a single access point to broadcast multiple ESSID utilizing a 
single BSSID.

I stumbled upon this because I was doing some testing where I was 
toggling the broadcastESSID setting of an access point and noticed that 
at one point I received two networks in the scan results from 
wpa_supplicant with the same BSSID.  One had a null ESSID, the other had 
it set.

I took a look at the hostap driver code (prism2_translate_scan() ) and 
it looks like if driver is configured for WPA, it will allow multiple 
scan results to be returned with the same BSSID.

My questions are:

1. How prevalent is this kind of configuration and does it really follow 
the 802.11 specification?

2. Does wpa_supplicant support this kind of configuration?

Thanks,
Tony Espy
Pepper Computer