[Dnsmasq-discuss] DHCP Issue

richardvoigt at gmail.com richardvoigt at gmail.com
Sun Jul 22 00:13:50 BST 2007


On 7/21/07, Simon Kelley <simon at thekelleys.org.uk> wrote:
>
> Steven wrote:
> > Hi,
> > I have a problem setting up a dhcp server using dnsmasq.
> >
> > Seems that the server is working fine but the client are not able to
> > get an ip address.
> > The interface on the server is configured to have a static IP address,
> > and on the client DHCP is used (obviously).
> > The client sends a DHCPDISCOVER packet, dnsmasq receives it and sends
> > a DHCPOFFER packet, but the client doesn't recognizes this packet (i
> > think).
> > With other dhcp server (as dhcp3-server) everything is working fine,
> > so i suspect this may be an issue with dnsmasq or my config file.
> >
> > I'm using Ubuntu, Feisty Fawn, Linux steven-laptop 2.6.20-16-generic
> > #2 SMP Thu Jun 7 20:19:32 UTC 2007 i686 GNU/Linux
> >
>
> The explanation for dhclient ignoring the DHCPOFFERS seems to be that
> the UDP checksum is incorrect. Is the Ubuntu system the client, or the
> server? The checksum problem seems to be  originating on the server, and
> if the server is running Ubuntu (or any Linux distro) then it's a kernel
> problem: on Linux dnsmasq delegates UDP and IP header creation to the
> kernel. If you are running dnsmasq on *BSD, then it could be a dnsmasq


What kind of network card on the server?  Some fancy ones support "checksum
offload" and this has bugs more often than not.


problem: on those platforms (some of) the UDP and IP headers are created
> by dnsmasq itself.
>
> Cheers,
>
> Simon.
>
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