option 51 ' dhcp-lease-time' vs other lease time statements

Darren Gamble darren.gamble at sjrb.ca
Tue Sep 19 18:14:21 UTC 2006

Hi Aaron,

Just to jump in here...

> David W. Hankins wrote:
> > If the client supplies option 51, the server selects a value close
> > the client-supplied value that falls between the min- and
> > config options.
> >
> > If the client does not supply option 51, the server does the same
> > except uses the default-lease-time (so it's a good idea to choose a
> > default that is somewhere inside your min/max range).
> >
> >
> So it's an indication of W2K's brain-deadedness then, that it stores a
> SERVER setting as "option 51" which option 51 is really a
> client-setting?

Sorry, that's not really correct.  It's used in both the request and
reply.  The client uses this field to request a lease time that it wants
(and it is optional to do so).  In the server reply, it's used to tell
the client what the actual lease time is.  The configuration options are
used on the server to determine what the actual lease time will be,
based on those options and the client's requested time, if any.  You can
honor the client's requested time, or just give it what you want

> I've chatted with the network engineer who maintains
> the W2K dhcp server here and he's confident that the figure stored as
> 'option 51' is in fact the server-supplied lease time, an analog of
> default-lease-time.

Well, he's right, it IS the server-supplied lease time.  The
default-lease-time is the value used if the client doesn't supply option

> Bizzare, but easy enough to work around for me.

If you want all of your clients to always have the same lease time, just
set the min, max and default lease times to be the same.

But no, no bugginess with Microsoft in this particular regard. :-)

Darren Gamble
Planner, Regional Services
Shaw Cablesystems GP
630 - 3rd Avenue SW
Calgary, Alberta, Canada
T2P 4L4
(403) 781-4948

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