[Dnsmasq-discuss] bridged interface gets wrong ip

Simon Kelley simon at thekelleys.org.uk
Sun Dec 30 20:30:40 GMT 2007


Daniel Mierswa wrote:
> On 30.12.2007 20:27, Simon Kelley:
>> My guess is that two interfaces with the same MAC address might be the
>> root of the confusion, but I can't explain exactly why. It would be
>> useful to see dnsmasq's lease database, in the file
>> /var/lib/misc/dnsmasq.leases
>>
>> Cheers,
>>
>> Simon.
> 
> here we go:
> 
> 1199084031 00:17:31:81:08:c8 10.0.0.17 Istari
> ff:00:00:00:08:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
> 1199084001 00:17:31:81:08:c8 10.0.0.16 *
> ff:00:00:00:07:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
> 1199083373 00:17:31:81:08:c8 10.0.0.14 *
> ff:00:00:00:03:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
> 1199074973 00:c0:a8:c3:fd:17 10.0.0.37 Rolf 01:00:c0:a8:c3:fd:17
> 1199070468 00:0c:6e:87:07:54 10.0.0.25 Orthanc
> ff:65:74:68:30:00:01:00:01:0e:97:af:d1:00:0c:6e:87:07:54
> 1199069263 00:80:77:10:fb:d4 10.0.0.29 brother-mfc-7820n *
> 1199073737 00:17:31:81:08:c8 10.0.0.15 *
> ff:65:74:68:30:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
> 
> 

Ah, that makes some sense. Your DHCP client is generating client-ids, 
which seem to vary in some way. (The client-ids are the last element on 
each line, wrapped in your example). Where client-ids exist, they are 
used instead of MAC addresses as unique identifiers for clients. There's 
a lease for 10.0.0.15 associated with 
ff:65:74:68:30:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
and when your host got 10.0.0.17, it presented a different client-id 
ff:00:00:00:08:00:01:00:01:0e:91:ed:a8:00:17:31:81:08:c8
Therefore it's a different host, and can't have 10.0.0.15. The error 
message is confusing, because it doesn't give the client-ids.

My guess is that the immediate solution to your problem is this:
stop dnsmasq, the  edit the file and remove the line with 10.0.0.15, 
then restart dnsmasq - you host will then get the correct address.

In the longer term, you should try and find out how the DHCP client it 
creating client-ids, and try and make them stable.

Cheers,

Simon.




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