Pseudo_IBSS mode issues

JAMES KABA jkaba at
Mon Dec 13 22:02:04 EST 2004

   I'd love to here other responses, but here's my 2 cents.

   I have seen this as well.  For the record, it is the cards in 
pseudo_ibss mode that are "misconfigured," since pseudo_ibss is not part 
of the IEEE 802.11 standard.  (It's a shame, too, because this "ad hoc 
demo mode" is such a useful mode.)

   The cards are still technically in pseudo_ibss mode, (i.e. they 
aren't generating any management frames), its just that they have 
updated their cell id to the one in the management frame they received 
from the node in "official ad hoc mode."  They can talk to other 
pseudo_ibss nodes that have been similarly corrupted, but not to 
pseudo_ibss nodes who are still in cell:00:00:00:00:00:00 and not to 
nodes in regular ad hoc mode.

   I think the real fix would be a simple firmware fix.  ( if mode == 
pseudo_ibss then don't listen to management frames.)  That is, nodes in 
pseudo_ibss mode should not create any management frames, NOR should 
they listen to management frames.  If anyone has any pull with the 
firmware driver developers, please ask them for this very simple fix!!!

   I have found that the key to not seeing this problem is to never have 
any nodes with the same ESSID be in anything other than ad_hoc mode! 
The way to do this is to get all your cards into pseudo_ibss mode before 
they are brought up.  --To do this, I use the pcmcia cardservices 
scripts instead of doing this configuration "by hand".  If you include 
these lines in you /etc/pcmcia/wireless.opts file
    IWPRIV="prism2_param 4 1"
you'll be in good shape.  These are the equivalent of what you mention 
below, but they are used to configure the card into pseudo_ibss mode 
before it is actually brought up.

(Note:  I've only seen this problem while trying to bootstrap/debug a 
new driver or something -- never in "steady state" -- so it seems to be 
pretty reliable.)


Anand R wrote:
> Hi -
>   I'm trying to setup an Ad-Hoc network. I'm trying to
> avoid the BSSID-partitioning problem by setting the
> card in pseudo_ibss mode. I'm using the following 2
> commands to do this:
> prism2_param wlan0 ptype 3
> prism2_param wlan0 pseudo_ibss 1
> I'm assuming these are the commands that I should be
> using to set a card in pseudo_ibss mode. Correct me if
> I'm wrong.
> The commands work fine if all the nodes within radio
> range are also in pseudo_ibss mode. But if there is
> some other node nearby with the same SSID, but NOT in
> pseudo_ibss mode, then the command does not seem to
> set the card in pseudo_ibss mode.
> I would like the nodes in pseudo_ibss mode not to get
> affected by other nodes that may be misconfigured (and
> hence not in pseudo_ibss mode).
> Here are the details of the card/firmware and driver
> I'm using:
> 2511 MP PLUS: 802.11b miniPCI Card
> (
> Firmware:
> Output from hostap_diag:
> NICID: id=0x8013 v1.0.0 (PRISM II (2.5) Mini-PCI (SST
> parallel flash))
> PRIID: id=0x0015 v1.1.1
> STAID: id=0x001f v1.7.4 (station firmware)
> HostapDriver version = 0.1.2
> Please help.
> Thanks,
> Anand
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