bridging trouble - far nodes not bridged

Scott Serr serrs at theserrs.net
Sun Apr 10 23:04:01 EDT 2005


Pedro Ramalhais wrote:

> Scott Serr wrote:
>
>> [I'm sorry if this seems like the wrong list to post to, but I bet you
>> guys do this implementation successfully all the time]
>>
>> I have 2 USR2450 wifi routers that are hacked and run LinuxAP.  (these
>> were earlier and wimpier equivalents of the WRT54G running an embedded
>> 386sx and prism2)  LinuxAP is kind of old: 2.4.20, hostap-0.0.4,
>> bridge-utils-0.9.6... all crammed in a 4MB firmware.
>>
>> My problem is:
>> Close neighbors can see eachother, but far neighbors can't.
>> No routing here, just bridging.
>> In a 192.168.x.x/24 network:
>> sparky (.4.1) -- usrAP (.4.243) -- usrSTA (.4.222) -- pc(.4.10)
>>                                  ^
>>                             wireless link
>>
>> sparky = UltraSparc/Linux with a Realtek 8190too
>> usrAP  = USR2450/Linux/hostap, wlan0 and eth0 in a bridge (br0 =
>> 192.168.4.243)
>> usrSTA = USR2450/Linux with wlan0 and eth0 in a bridge (br0 =
>> 192.168.4.222)
>> pc     = XP with a Netgear FA310 NIC
>>
>> The AP and STA are communicating fine, the wireless layer doesn't seem
>> to be the problem. Sparky can ping usrAP and usrSTA, but not pc. pc
>> can ping usrSTA, but not usrAP or sparky. usrSTA can ping EVERYBODY.
>> usrAP can ping everyone but pc.
>>
>> usrAP and usrSTA bridges both have stp on, hw ether macs set the same on
>> eth0 and wlan0 before bound in br0.
>> I think my problem is with usrSTA, since when "sitting there" I can get
>> everywhere.
>>
>> Has anyone seen anything like this?  I've got about 8 hours in this
>> problem now, if I find the answer -- I'll post it.
>>
>> Thanks,
>> Scott
>
>
> As far as i can remember wireless stations in Managed mode can't
> forward packets on behalf of others because it's not supported in the
> IEEE 802.11 frame format, so, forwarding or bridging doesn't work. The
> only way to achieve what you want is to either do NAT on the usrSTA
> side or use WDS (Wireless Distributed System). For WDS you need prism2
> station firmware (IIRC) bigger than 1.7.4.
>
Ugh.  I think you are right.  I setup a mock-up on real computer (STA)
and a off-the-shelf AP, same thing.  I remember reading that the WDS
that prism2 does is a hack and not compatible with commercial WDS
systems... but I didn't know the STA mode could not forward packets on
behalf of others.

I guess that is why what I was trying wasn't a standard setup in
LinuxAP.  <sigh>  Back to fiddling with this old version of WDS, got it
working about a year ago.

Thanks so much for keeping me from going insane,
Scott




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