[Dnsmasq-discuss] Re: DHCP: different IPs for same same MAC

Sven Köhler skoehler at upb.de
Sun May 4 21:59:51 BST 2008


>>  here's the leases file from a currently running dnsmasq installation:
>>  86400 00:12:f0:a1:81:7d 10.1.2.233 bert 01:00:12:f0:a1:81:7d
>>  86400 00:12:f0:a1:81:7d 10.1.2.22 *
>> ff:65:74:68:31:00:01:00:01:0e:91:06:82:00:00:f0:7a:14:04
>>
>>  How can that be? Same MAC-addresses, but different IPs?
>>
>>  Well, if i boot Linux on this comuter, it get's the 10.1.2.22.
>>  If i boot Windows, then it get's the 10.1.2.233. Why is that?
>>  (BTW: if i delete the leases file, restart dnsmasq, and boot windows first,
>> then windows get's the 22 and linux get's the 233).
> 
> One is sending a client ID and one is not.  The fact that switching
> them reverses it seems odd to me, since I would have a possible
> explanation if it didn't...

My guess is, that the two DHCP-requests by the two OS differ - and 
dnsmasq compares them, and then says: oh, different DHCP request, so 
let's give him a different IP (which seems completely beyond the idea of 
DHCP to me, since leases-file should only be a MAC->IP mapping).

> Is there an entry in /etc/hosts or /etc/ethers?

No

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