Wireless DHCP issues

Werner Almesberger werner at openmoko.org
Thu Feb 5 23:26:16 CET 2009

"Marco Trevisan (Trevi?o)" wrote:
>> Maybe check if  wmiconfig -i eth0 --power maxperf  does something.
>> After all, we know that it has some mysterious but apparently very
>> reproducible effect on this kind of oddities.
> I've tried with it too, but nothing changes.

Good ! I find that --power maxperf business highly mystifying.
So it's nice if we don't have this kind of spookiness going on
here ;-)

> Myabe this is due to the card I'm using for monitoring? I've an ipw2200
> and it has always worked when it come to monitoring wireless traffic.

Hmm, I don't have an IPW2200. http://linuxwireless.org/en/users/Drivers
says that is its monitor mode has some limitations, but I couldn't
find any details.

I'll give my collection of mac80211 cards a try.

> If you want I can send you my .pcap dump taken with airodump, but it
> basically says the same that you can figure from the dhcp tools logs.

If you could mail me the capture file of the session with udhcpc,
that may be useful. Perhaps there's some indication why it didn't
like the first two offers.

>  - There are issues with the DHCP and wpa that unfortunately I wasn't
>    able to study.

Hmm, Mickey told me today that there's a discussion about DHCP
problems with FSO MS5 on the support list. From what I gather there,
it might be DHCP racing with association. (Plus udhcpc doing things
that increase the confusion.) But that doesn't seem to be the problem
in your case since you're running things manually anyway.

> I should find an open AP that doesn't give me an IP

So the DHCP failure also happens without encryption ?

> (one is at my pub,
> but, you know... I can't go there to monitor wireless packages :P),

Hmm, why not ? Sounds like a comfty enough setting for doing a bit of
network debugging and/or a good excuse for spending more time at the
pub ;-) If you're concered about other people's privacy, you can
always filter by MAC address.

- Werner

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