[Dnsmasq-discuss] dnsmasq gives wrong IP if using client id

richardvoigt at gmail.com richardvoigt at gmail.com
Wed Feb 27 06:11:34 GMT 2008

On Wed, Feb 27, 2008 at 1:15 AM, Joerg Mechnich
<joerg.mechnich at gmail.com> wrote:
> Hi,
>  I am running dnsmasq 2.40 on Debian testing arm5vtel and have the
>  following problem:
>  My laptop is used in the local network either on wireless or wired
>  ethernet. So I am using something like
>  dhcp-host=id:00:78:56:34:12,badwolf.localnet in dnsmasq.conf and
>  badwolf.localnet             in /etc/hosts
>  for client identification (i.e. use client id instead of MAC address) so
>  that I can get the same ip address on both interfaces.
>  This basically works *but* when the dhcp client tries to reactivate a
>  lease from a different network (e.g. if I come home from work where the
>  machine had a different IP) it gets an arbitrary ip from the DHCP pool.

If you have switched between wired and wireless, and the lease given
to the other adapter has not yet expired, then the address is not
available and a new address will be given out.

My suggestion: set your laptop to bridge the two interfaces and enable
spanning tree.  That way only one MAC address will be seen by dnsmasq
regardless of whether you are connected wirelessly or tethered.

>  I have to manually delete the leases on the client (dhcp3-client 3.0.6),
>  change/remove the client entry in dnsmasq.leases and restart dnsmasq.
>  As far as I can tell, this does not happen when using the MAC address
>  for client identification.
>  So my suspicion is that the requested ip address in the DHCP Discover
>  packet somehow confuses dnsmasq if one uses the client id for client
>  identification, I would expect dnsmasq to ignore it.
>  Is it possible to force the "correct" behaviour or would I have to
>  configure my client differently?
>  Maybe this isn't even a bug but a feature that I don't understand ;)
>  Cheers,
>  Joerg
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