Cleanup leases?

King, Michael MKing at
Tue Sep 26 16:19:21 UTC 2006

Normally we go for 8 days.  (It's the default lease length in Microsoft
DHCP, and we just kept the convention for consistency sake)

However, our residence halls are 7200  (2hours) with a max of 72000 (20
hours) because this was what the system integrator used, and we didn't
feel like changing it.

-----Original Message-----
From: dhcp-users-bounce at [mailto:dhcp-users-bounce at] On
Behalf Of Sean Kelly
Sent: Tuesday, September 26, 2006 11:38 AM
To: dhcp-users at
Subject: Re: Cleanup leases?

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 long?

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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