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  1. #1

    transparent wireless bridging, will this work?

    Hey everyone, I'm trying to setup a transparent wireless bridge, but traffic is only making it to 2 of the 3 interfaces.. I could really use some help here.

    Heres the situation, I am trying to "extend" the range of my ap. I have a laptop with two wireless cards ( 1 atheros, 1 intel 3945abg ). I am putting one interface into ap mode, the other into managed, bridging the connection, but traffic is only seen on nic hosting the ap, and the bridge. the interface in managed mode isn't receiving any of the traffic. here is how i'm doing it:

    ifconfig ath0 down
    wlanconfig ath0 destroy
    wlanconfig ath0 create wlandev wifi0 wlanmode master (master or ap?same?)
    ifconfig wlan0 up
    iwconfig wlan0 essid "office" key xxxxxxxxxx
    ifconfig ath0 up
    iwconfig ath0 essid "extension"

    brctl addbr br0
    brctl addif br0 wlan0
    brctl addif br0 ath0
    ifconfig br0 up
    dhclient br0 (or ifconfig br0 netmask broadcast

    Now if a client connects to "extension" and requests an ip address via dhcp, i can see traffic (via wireshark) on ath0(the ap nic) and br0; however, wlan0(the nic in managed mode connected to "office") doesn't see anything.

    some of my key questions are :
    1. does wlan0 need to be associated w/ the "office" ap? that only happens when i give it an ip would i need to assign it one to get associated then set my ip on wlan0 again?
    2. do i need to set a default route for anything, br0 maybe?
    # route add default gw br0
    3. my ap currently uses stp ( i can see from the wireshark output ), so i'm assuming i need : brctl br0 stp on ??

    Thanks so much for any help, it is greatly appreciated as this has been going unsuccessfully for me for a while.

  2. #2
    Hey everyone, heres an update:

    I'm at the 97% mark and just wanted to ask a quick question:

    I have wireless transparent bridging setup, and my laptop acts as an extension of the ap. my other computer can see my laptops network, join it, and traffic makes it all the way across the bridge in my laptop over to the connected computer. The only problem is it seems that no other hosts can communicate with the default gateway ( the actual ap ). broadcasts are seen (via wireshark), and i can see network traffic. But when a connected host requests and address via dhcp, no reply from the default gw. when i statically assign an ip and try to ping the default gw, there is only an arp request for, no responce. So it seems like nothing can communicate with the default gw other than my laptop.

    i found out at that :
    "This is a known problem, and it is not caused by the bridge code. Many wireless cards don't allow spoofing of the source address. It is a firmware restriction with some chipsets."
    So it seems maybe my card cannot spoof its MAC.

    i can use dhclient and get an ip address for br0 when it is using the same MAC as wlan0 ( the interface connected to the "office" ap ), but when i use macchanger and set it to my ath0 (interface used as an "extension") dhclient fails to receive an ip.

    So i'm thinking that only the mac associated w/ the "office" ap can communicate w/ the default gw, apparently being associated with me and then being bridged accross does not work (unless i have a prism chipset according to

    So...should I use NAT to take all the traffic from ath0(ap mode) and make it look like its coming from me. again using the bridge and everything. so basically all this requires is wireless transparent bridging and NAT?

    does that make sence, is that the best way to go about it? also, any point in the right direction to a specific NAT program or site would be great as i've never set up NAT on my box before.

    thanks everyone i really appreciate the help, sorry for the length, thanks!

  3. #3
    Any update on this post? I am trying to do something similar, except that I am trying to bridge the station wireless interface to an Ethernet interface. If the issue is MAC Spoofing, could this be done with ebtables? From ebtables you can essentially perform MAC level NAT, so that everything from the Ethernet side would look like it was coming from the wireless card.

    I will set this up and report back my results. I am also starting to test with WDS, some success, but I can not find enough detail on wireless AP to give me the warm fuzzy that this will always work.

    This question is being raised in multiple forums, but I have not been able to find an answer. Other than references to the prism chip set. But I have not been able to find a "how to" or any evidence that anyone is actually doing this with a prism chip set.




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