DHCP "static" assignments

Peter Rathlev peter at rathlev.dk
Sat Aug 10 07:47:46 UTC 2013

On Fri, 2013-08-09 at 12:58 +0100, Simon Hobson wrote:
>  Once a lease is expired, it's then eligable for re-use. So if (in this
>  case) a printer is switched off for a long time, it's address may well
>  be allocated to another device before it gets switched back on again.
>  Addresses are re-used on a "least recently used" basis, and whether
>  you have a problem will depend on how long the device is off for, how
>  many free addresses you have*, and your churn rate.

We had three clients and nothing else on a /24 network and they kept
getting assigned new addresses if the old lease was expired, e.g. over a
weekend. The client identifiers didn't change, neither according to the
lease file on the server nor according to tcpdump. When we changed the
lease-time to 3 days instead they kept their addresses across weekends.

I haven't really investigated this since it's not really a problem. The
lease-time increase was primarily because there wasn't much churn on
that network, same clients all the time. That they changed addresses
every week was only a nuisance. Dynamic DNS worked fine.


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