wpa_supplicant, hostap & virtual access points?

Jim Thompson jim at netgate.com
Tue Mar 14 21:12:05 EST 2006

Tony Espy wrote:

>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?
its within 802.11 spec.  (I had the idea in 1999 or possibly 1998.)  Its
(correctly) implemented
in the madwifi drive and the devicescape code.

You can do multiple BSSIDs on some chipsets too.

>2. Does wpa_supplicant support this kind of configuration?
no, but nothing prevents you running two copies.

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