[PLUG] Bizarre network problem

Russell Senior russell at personaltelco.net
Wed Sep 5 18:03:28 UTC 2007


>>>>> "Fedor" == Fedor Pikus <fpikus at gmail.com> writes:

Fedor> Ok, so the conclusion seems to be that if I put the bridge into
Fedor> "AP client" mode, I can have only one computer connected to it,
Fedor> not two.  This appears to be consistent with the observations:
Fedor> one of the three computers on the switch behind the bridge will
Fedor> work, the other two won't, and if I powercycle the bridge then
Fedor> the different one may start working (but the other one will
Fedor> stop working).

Yes.  If the wireless client is something hackable like a Linksys
WRT54GL or the like, you can reflash with OpenWrt or similar and set
it up as a NAT'ing client too.  That will work for more than one
device, but then it isn't bridging (if you really need bridging).  To
do "wireless bridging" for more than one device, you really want WDS,
I think.

For a little more detail, for full-generality bridging you need 4 mac
addresses (they have official names, which i've forgotten and am too
lazy to look up, and also I am doing this from memory and may have
some of it slightly wrong, so bear with me and checkup on the details
if it matters to you):

  SRC
  DEST
  STA
  AP

SRC and DEST are the normal ethernet mac addresses.  STA and AP are
the mac addresses of the wireless devices (STA being the client, AP
being the master-mode device).  In master/client mode only three are
used, SRC and STA being conflated.  So, from the master side, when
someone wants to send a packet back, all it has is the STA mac addr
and not the mac addr on the other side of the client bridge.  It can
work with one device by assuming that the packets are for that device
and passing it along.  In WDS, all four mac addrs are used, so
bridging works.


-- 
Russell Senior, Secretary
russell at personaltelco.net



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