same ip to the same mac ?

[Simon Hobson]

Petre Bandac wrote:

>while parsing my dhcpd logs, I have noticed a strange thing: apparently,
>the same ip gets somehow "reserved" for the same mac address
>
>thus, the client always gets the same ip everytime it connects (which I
>want to prevent)

Yes this is the design of the ISC server and is (IIRC) required by 
the RFC. Certain other servers are non compliant in this area (along 
with a few others).

It is why you will find lease entries in the leases file for expired 
leases, so the server can keep track of what leases it has given out 
in the past.

The algorithm for choosing a lease for a client is (roughly) :

Has this client had a lease in it's current subnet before ?
   If so, then give it the last address it had

Is there an unused address ?
   If so then allocate a previously unused address

Find a previously used but currently free address and offer that. 
This is done on a least recently used basis, and obviously once the 
address has been reused like this then the link with it's previous 
usage is lost.


Now, why do you want the address to keep changing ?