capturing beacon frames on my wireless card

This is a discussion on capturing beacon frames on my wireless card within the Networking/Device Communication forums, part of the General Programming Boards category; Hi all, I have a wireless (802.11b) router Access Point and my laptop connected together. As i can see in ...

  1. #1
    Registered User
    Join Date
    Aug 2010
    Posts
    23

    capturing beacon frames on my wireless card

    Hi all,

    I have a wireless (802.11b) router Access Point and my laptop connected together. As i can see in the configuration of the router there should be a beacon frame sent every 100ms on my AP. I would like to see all these control,management frames sent from the AP to the stations.

    Now, in order to see those packets I need to set my wireless card on monitor mode and hope the the drivers that i have for the wireless card can give me this information. I have used tcpdump and wireshark to capture that but in both cases i couldnt see any of these frames.
    Here is what i ve tried.
    First wireless card

    lsusb:
    Bus 001 Device 002: ID 050d:905b Belkin Components F5D9050 ver 3 Wireless Adapter

    in tcpdump i check my devices by
    sudo tcpdump -D
    1.eth0
    2.wmaster0
    3.wlan0
    4.ppp0
    5.wmaster1
    6.wlan2
    7.any (Pseudo-device that captures on all interfaces)
    8.lo

    My Usb card is wlan2, and it also introduced the wmaster1 entrance in this command, not sure about the meaning of that. Next i tried to set my card in monitor mode
    sudo tcpdump -I wlan2

    or sudo tcpdump -I wmaster1

    in both cases the output is
    tcpdump: eth0: That device doesn't support monitor mode

    Because i couldnt find a solution for that, i move to wireshark and try to set the cards to capture the frames. In wireshark, capture interfaces i can see that the usb1 interface (the one i have my wireless card connected to) is adding up received packets. If i receive this packets the output is something like below which i do not understand.

    URB_BULK
    URB_CONTROL
    URB_CONTROL
    URB_CONTROL
    ....

    Second thing that i tried with wireshark is to set the interface of wmaster1 disabling the option of "hide capture info dialog" and from "Edit/preference/protocols" i set it to 802.11 frames.

    In this case i am able to see some 802.11 packets sent with no data from the Computer to the AP but they have no major meaning. Also it might worth to mention that i never see a packet sent from the AP mac origin to the Pc with no data value (which could be some controlling packet).

    So could somebody guide me what i am doing wrong?

    Thanks

  2. #2
    Registered User
    Join Date
    Aug 2010
    Posts
    23
    So far, all i can say is that the network cards do not support monitoring mode and therefore you can not see other packets nor frame values. Next time I ll have to double check before getting a wireless card

    Thanks

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