Doubt On Scanning Hidden AP

Raghavendra s.raghu at samsung.com
Fri Apr 18 08:39:36 EDT 2008


Hi Jouni,

 In your below response to my query you have mentioned, (i.e., wpa_supplicant is just configuring the SSID and security policy).

Does that means it is not possible to scan and display result of Hidden APs using wpa_supplicant. Becoz whatever you mentioned above is while getting conneted/associated, if we mention AP SSID then it will try to connect.

I my case, I have a following config file using which I will enable wpa_supplicant.
-----------wpa_supplicant.conf start-----
ctrl_interface=/var/run/wpa_supplicant
ap_scan=2
----------wpa_supplicant.conf ends-----



I am enabling wpa_supplicant with above configuration. Then using wpa_cli, I issue 'scan' command and then 'scan_result', to get scan result.
Before enabling wpa_supplicant I have 'Disabled SSID Broadcast' feature on my AP.
If I 'Enable SSID Broadcast' then I am getting my AP info in scan result. But If I 'Disable SSID Broadcast' I am not getting my AP info in scan result.
So I would like to know how can I get information of a AP in which SSID Broadcast is Disabled.

-Raghu.



Date: Sat, 12 Apr 2008 18:08:01 +0300
From: Jouni Malinen <j at w1.fi>
Subject: Re: Doubt On Scanning Hidden AP
To: hostap at lists.shmoo.com
Message-ID: <20080412150800.GA7709 at jm.kir.nu>
Content-Type: text/plain; charset=us-ascii

On Fri, Apr 11, 2008 at 09:58:47AM +0530, Raghavendra wrote:

>    In some spec I came across the word "Scanning Hidden AP". 
> 
>  Can any tell me what is this hidden AP means?
> 
>  Also whether wpa supplicant is capable of doing that?
>  If so how to achieve it in wpa supplicant..I mean is there any special configuration that I have to do for scanning hidden AP using wpa supplicant?

In most cases, wpa_supplicant itself does not perform the scan; this is
left for the driver/firmware. In case of "hidden SSID" passive scanning
(just listening for Beacon frames) does not find the SSID for the AP and
an active scan with a specific SSID (i.e., sending Probe Request frames
with a specified SSID) is needed. wpa_supplicant can instruct the
driver/firmware to do this with scan_ssid=1 option in ap_scan=1 mode
(not all drivers support this, though). Alternatively, ap_scan=2 mode
can be used to leave all details of AP selection to the dirver/firmware
(i.e., wpa_supplicant is just configuring the SSID and security policy).

-- 
Jouni Malinen                                            PGP id EFC895FA
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