Multiple SSIDs on a single BSSID (was: Multiple SSID)

Jouni Malinen j at
Tue Nov 6 23:49:55 EST 2007

On Thu, Oct 25, 2007 at 09:25:57PM +0200, Johannes Berg wrote:

> But let's discuss the starting point first; I'm thinking that multiple
> SSIDs on the same BSSID are implemented by an AP by treating all
> stations as belonging to the same BSS wrt. QoS, AID assignment etc.,
> hiding the SSID in beacons and then keying off the SSID given in probe
> requests and association requests to determine which network the station
> wants to use. Different group keys can be used to separate the networks.

> From the mac80211 perspective it is pretty trivial:
>  - create a VLAN interface for each SSID
>  - beacon with zero-length SSID
>  - put stations into correct VLAN depending on the SSID they used in
>    their association request frame
> If you need help with the kernel side I'm certainly willing to give
> advice and help.

This used to be supported in Devicescape code.. Was something removed
from mac80211 to make this not work?

> It seems to me that the hostapd changes would essentially be:
>  - allow having multiple SSIDs
>  - keep some sort of SSID-structure for each BSS
>  - assign stations to vlans depending on the SSID they used
> I do not, however, know whether the internal hostapd structures
> facilitate this let alone how to implement it.

I've implemented this in the Devicescape version, but it looks like it
was not merged into the open source version or at least not all parts of
it were merged.. I don't remember why, but this may have been because
multi-BSS support is superior to multi-SSID in almost everything and
there are some major problems in trying to use single Beacon frame to
support different security policies (many existing clients do not like
it at all if the Privacy flag or WPA/RSN IE in Beacon frame do not match
with the one in Probe Response for the SSID they are trying to use).

Jouni Malinen                                            PGP id EFC895FA

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