[lug] ARP packets not seen?

Tkil tkil at scrye.com
Sun Jul 19 02:32:10 MDT 2009

My new project involves arguing with an "embedded"-class box.  I'm
trying to get it talking to my linux box over IP, and not having much

I currently have three boxes connected to a single switch (with their
associated, manually-assigned IP addrs):

  a. linux box (fedora 11)
  b. embedded box 
  c. windows box (xp pro)

The embedded box can ping the XP box, but not the linux box.  The
windows box can't ping the Linux box (except I got one reply out of
literally hundreds of requests; no idea WTF is up with that.)

(The embedded box runs in polling mode, so it isn't usually waiting
for ping packets, so neither of the other two boxes can ping it, and
that's to be expected.)

What's bugging me is that the XP box seems to be able to behave
correctly on the network, while the linux box is misbehaving.

(Said linux box also has a second interface, the wireless one that
connects it to the rest of the world; I'll experiment with the
mini-network without that wireless interface, and see what's up.)

Running 'tcpdump' on the linux box: it sees the ARP requests, and
replies with "is-at" packets appropriately -- but neither of the other
two boxes seem to see those packets!  Using 'wireshark' on XP, I can
see that it's asking the right ARP question (and that the embedded box
also asks the correct question) ... but I never see the reply.

I'm guessing that either I have a defective switch (Linksys 5-port
10/100 cheap-ass switch, so not outside the realm of possibility), or
that something on the linux box is keeping those ARP replies from
reaching the switch in the first place.

Any ideas?


p.s. I also noticed that doing a manual configuration on the linux
     box, and then bringing the interface down then up, made a entry
     in the routing table for ... no idea why, and I worry
     that it's somehow sending packets off into the weeds.

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