multiple IPs to single machine

Simon Hobson dhcp1 at
Tue Sep 5 22:39:08 UTC 2006

dhcp-admin at wrote:

>Is there an easy way to cause the dhcp server to not give out a new 
>IP to a machine that already has (or had) a lease on the same 
>segment - based on MAC addresses?

Short answer is that it won't - unless the client identifier changes.

Longer answer, the client-id is the primary key for the database and 
the mac address is only used if the client-id is absent. If the 
client-id changes then as far as the server is concerned it is a 
different client. This mainly affects machines that boot into several 
OSs, normally including Windows - everything but Windows would 
typically have no client-id, while Windows would insert the mac 

Someone was working on a patch to change the behaviour so that in the 
absence of a client-id, the server would insert the mac address (as 
per the Windows client) so that multi-booting systems would get the 
same address. I don't know if that patch is still valid.

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