[Dnsmasq-discuss] Re: DHCP: different IPs for same same MAC
Jan 'RedBully' Seiffert
redbully at cc.fh-luh.de
Mon May 5 02:57:06 BST 2008
Sven Köhler wrote:
>>> 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 *
>>> 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
>>> 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).
In dnsmasq, client-ID overrides MAC-Address, and thats the difference
between the two requests.
I was bitten by this when my linux-distro updated the dhcpc, now sending
a random id, when sending none before...
so you want to change in your dnsmasq.conf:
dhcp-host=00:00:F0:7A:14:04 , 10.1.2.21 #bert
dhcp-host=00:00:F0:7A:14:04 , id:* , 10.1.2.21 #bert
The Theorem Theorem: If If, Then Then.
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