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Re: Help needed with ethernet configuration - dhclient seems to ignore DHCPOFFER

On Sun, Aug 17, 2003 at 10:20:19PM +0200, Komáromi Eszter wrote:
> Thanks for the help, David,
> I managed to find your thread in the archives. I  get some weird packets
> indeed, not arp though. Here's tcpdump's output (tcpdump -s 2000 -nXe -i
> eth0):

> 16:20:58.686564 0:0:77:94:e1:a 0:e0:29:9a:6b:ec 0800 363:
> >  hops:1 xid:0xab353177 Y:
> G: vend-rfc1048 DHCP:OFFER SID: LT:3600
> SM: BR: DG: DN:"chello.hu"
> NS:,,
> ACKT: (DF) [tos 0x1]
> 16:21:02.139112 0:e0:29:9a:6b:ec ff:ff:ff:ff:ff:ff 0800 342: >
>  xid:0xab353177 vend-rfc1048 DHCP:REQUEST
> SID: RQ: CID:00:e0:29:9a:6b:ec
> PR:SM+BR+TZ+DG+DN+NS+HN [tos 0x10]

If you look carefully, you see an offer (SID-field) for the address Then, your system does a request (again, SID) for that
same address. What I'm a bit puzzled about, is that I see _nothing_ in
return from your logs, only some random chatter between other computers.
And the offer was _from_ _to_, _not_
you. I'm puzzled. You might want to try a number of things:

  - Boot windows. Try to get an IP address. If you don't get one,
    contact your ISP (chello?)
  - If you _do_ get one, _and_ have an other computer running linux, try
    putting that one in between (or you could try a hub) and examine the
    packets that go back and forth. Depending on your setup, this might
    be a very impracticable solution.
  - Run tcpdump -w file and send me the file. Please don't wait ten
    minutes before ending tcpdump, ;-) I can analyse the file with
    different options, pipe it through dhcpdump, etc.
  - Just assume that you won't steal another's IP and read the SID-field
    (in this case, quit tcpdump, leave dhclient running
    but do ifconfig eth0 See what happens... This is
    only a short-term solution!!!!!!!

HTH, David

Happy Birthday, Debian!
August 16, 1993

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