Cleanup leases?

Sean Kelly smkelly at
Tue Sep 26 15:38:05 UTC 2006

On Tue, Sep 26, 2006 at 10:26:07AM -0400, Jeff A. Earickson wrote:
> Well, there are times when lease pools can fill up at edu site because
> of "big turnover" lease events.  For instance, our dorm lease times are
> normally 30 days, which works well through out the school year.  But in

Thirty days?! What was the justification behind making your lease times so

Our default lease time across the entire network is 2 hours, with a maximum
lease time of four hours. This includes all residence halls that reside on
our network. THe theory is that since DHCP attempts to hand out the same
addresses to returning clients, and since clients generally renew at around
the halfway point of their lease's lifetime, we don't gain much from having
longer lease times.

The only advantage I see to really long lease times is that if DHCP goes down,
fewer clients are going to be impacted. However, this can be mitigated by
using DHCP failover. Furthermore, by having shorter lease times we avoid
the specific problem you mention where high turnover causes us to run out
of addresses.

I'd be curious to see what people set their lease times to, and what their
reasoning is for it.

Sean M. Kelly
Unix Systems Architect
Division of Information Technology
Creighton University
(402) 280-2264
AIM: smkellyg5

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