Periodic assignment of unique IP address

Simon Hobson dhcp1 at
Thu Nov 29 23:36:46 UTC 2007

Siraj Shaikh wrote:

>  > >May I just add here, we are not interested in assigning a particular
>>  >unique IP address (at every renewal) - just whatever is available from
>>  >the pool (which we will set accordingly ofcourse).
>>  Change the client-id when you want a new address - the server will
>>  then identify it as a new client and give it a different address.
>>  This is because the client-id is the primary database key, the mac
>>  address is only used if the client-id is not present.
>Thank you for this clarification: I think this solves it. The only
>thing we will need to do then is come up with a list/range of
>client-ids which can then be mapped onto different ip addresses.

No need - as long as you keep changing the id, you will keep getting 
different addresses. At least, with the ISC server you will - I don't 
know about others (the MS one isn't RFC compliant). It would be 
sufficient to just keep incrementing it - as in :


and so on.

Just don't do it too often or you run the risk of exhausting your 
address pools by tying up too many addresses with unexpired leases.

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