bridging trouble - far nodes not bridged

Pedro Ramalhais ramalhais at serrado.net
Sun Apr 10 20:25:20 EDT 2005


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.

-- 
Pedro Ramalhais



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