Re: [gentoo-embedded] dhcp across segments with dnsmasq?

[Natanael Copa <natanael.copa@gmail.com>]

On Mon, 2006-06-26 at 16:16 -0500, mjinks@uchicago.edu wrote:
> We have a big old Dell running RedHat, which does nothing (any more) but
> serve DHCP for a number of labs around our campus.  We thought it would
> be an ideal candidate for replacement with a home-rolled GNAP machine
> using dnsmasq's DHCP service.

[ snip ]

> A little tcpdumping shows some differences between the old (RedHat) box
> and the new (GNAP) system.  In this example, "msfc-ri-v17.uchicago.edu"
> is the router which serves our DHCP client; "dell-test-03.uchicago.edu"
> is the DHCP client; and "bonzai.uchicago.edu" houses the DHCP server.
> tcpdump is running on bonzai:
> 
> 14:42:27.985373 msfc-ri-v17.uchicago.edu.bootps > bonzai.uchicago.edu.bootps:  (request) hops:1 xid:0x20dcf2e1 secs:4 flags:0x8000 G:msfc-ri-v17.uchicago.edu ether 0:f:1f:dc:f2:e1 [|bootp]
> 14:42:27.986066 bonzai.uchicago.edu.bootps > msfc-ri-v17.uchicago.edu.bootps:  (reply) hops:1 xid:0x20dcf2e1 secs:4 flags:0x8000 Y:dell-test-03.uchicago.edu S:bonzai.uchicago.edu G:msfc-ri-v17.uchicago.edu ether 0:f:1f:dc:f2:e1 [|bootp] (DF)
> 
> Now here's an example of the same case, except that the hardware acting
> as bonzai.uchicago.edu is now our GNAP machine:
> 
> 01:06:27.601181 IP msfc-ri-v17.uchicago.edu.bootps > bonzai.uchicago.edu.bootps: BOOTP/DHCP, Request [|bootp]
> 
> The GNAP box doesn't issue a response, apparently because it can't see
> that the request is coming from one of its listed DHCP clients.

Have you tried running dhcpd on the GNAP box?

> So, does anybody know what might be going on here?  I don't think that
> dnsmasq is (necessarily) the culprit, since tcpdump shows more
> information in the case of the packets dumped on the RedHat machine.  

To me it looks like its dnsmasq. The request packet arrives to your GNAP
box but dnsmasq is never responding.

> Is
> this a difference, maybe, in the uclibc network handling?  Do I need to
> tweak my kernel?  Am I just crazy?
> 
> Thanks for any thoughts.

Try this one:
http://thekelleys.org.uk/dnsmasq/docs/FAQ

Look for this part:
Q: This new DHCP server is well and good, but it doesn't work for me.
   What's the problem?


--
Natanael Copa

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