Cleanup leases?

David W. Hankins David_Hankins at
Tue Sep 26 20:34:36 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
> the summer we have summer programs with visitors that come and go.  If
> we forget to lower our lease time at the beginning of August, then we
> run out of leases in the dorms come September because old info from 
> summer visitors is still in the lease pool.  Hence my perl script to
> clean dorm leases by force at the end of August before students return.

It might be nice if the lease time offered by the server were not a
fixed value, but were more intelligently chosen.

Christof Chen submitted patches we put in 3.1.0 which allow the
server to reduce the lease-time it offers (a sort of "panic mode")
when it starts to run low on leases.  The hope is that it increases
the 'return rate' of leases.

Another interesting thing might be to only offer a client a lease
time that is as long as the client has been observed on the network
upon that lease, with a minimum.  So you get ~1 hour to start, then
if the client returns, ~1.5 hours, so on, until you either reach
the client's requested lease-time (if they're polite enough to
provide one), or some upper ceilling (like 30 days).

Sites like college compuses might also want a 'gold rush' mode,
for when students first arrive at the start of the year (you'd
want to give out the long lease time just to reduce DHCP traffic).

Of course, it would also make failover potential-expiry calculations
/much/ more entertaining.

ISC Training!  October 16-20, 2006, in the San Francisco Bay Area,
covering topics from DNS to DDNS & DHCP.  Email training at
David W. Hankins	"If you don't do it right the first time,
Software Engineer		you'll just have to do it again."
Internet Systems Consortium, Inc.	-- Jack T. Hankins

More information about the dhcp-users mailing list