DHCP lease order

Brendan Forsyth bff at pvhs.org
Fri Jan 23 21:09:08 UTC 2009

To be honest the request didn't make sense to me either but I had to ask.  I'll inquire as to the 
reason and respond back to the list.  
Thanks for the response.
Brendan Forsyth
Senior System Administrator
Poudre Valley Health Care
3702 Automation Way
Fort Collins CO 80525
bff at pvhs.org 
(970) 495-7731 office
(970) 689-2503 cell

>>> Simon Hobson <dhcp1 at thehobsons.co.uk> 1/23/2009 1:20 PM >>>
Brendan Forsyth wrote:
>Our dhcp server gives out leases from the end of the subnet back to 
>the beginning.
>Is it possible to reverse this ordering?

Actually, the ISC server allocates (never used before) addresses in 
an implementation specific and undocumented order - it just so 
happens that AT THE MOMENT it does it "top down".

That is only the case when there are addresses that have never been 
used. Once there are no such addresses, it will reclaim expired 
leases in a least recently used manner and normally addresses will 
then appear to be allocated randomly.

There is no direct way to influence allocation order of addresses, 
but you can fudge the issue if you really care (why ?). If you write 
a script that will create dummy leases for all available addresses, 
then you can determine the order that addresses will be allocated in 
future by simply ordering the expiry date/time of each dummy lease.

The obvious question is why do you want a specific order ? There 
isn't really any good reason other than your are trying to do 
something that probably has a another way.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.
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