dissecting DHCP - Q3

[Daniel Duarte]

Hello all,

Regarding this topic, I have a small question. In my network topology,
I would like that the lease time would always have the same time,
regardless of the servers' state.

To do so, I think I could configure min-lease-time = max-lease-time =
default-lease-time = MCLT.

This seems simple, however I wounder if there if there's some scenario
of failure on one of the failover peers where this configuration could
be dangerous or at least not recommended.

Thanks for your help,
Daniel Duarte


On Wed, Mar 18, 2009 at 5:28 AM, Glenn Satchell
<Glenn.Satchell at uniq.com.au> wrote:
>
> Ok, it's slightly more complicated than that. :)
>
> Have a look at the dhcpd.conf man page and scroll down to the sections
> titled "DHCP FAILOVER", "FAILOVER STARTUP" and "The mclt statement".
>
> With failover, a server is allowed to hand out a lease of up to mclt
> seconds without contacting the other failover peer. So, the dhcp server
> hands out an initial lease of mclt seconds. Then the client communicates
> this to the partner. This allows the server to respond quickly to the
> initial request without waiting for the failover peer to respond. When
> the client renews this short lease, if the server has communicated with
> the peer, it hands out a lease of default length.
>
> regards,
> -glenn
>
> >From: "Defryn, Guy" <G.P.Defryn at massey.ac.nz>
> >To: Glenn Satchell <Glenn.Satchell at uniq.com.au>, Users of ISC DHCP
> <dhcp-users at lists.isc.org>
> >Date: Wed, 18 Mar 2009 15:58:32 +1300
> >Subject: RE: dissecting DHCP - Q3
> >
> >Thanks Glenn,
> >
> >That makes sense.
> >In the mean time the client has obtained a lease for a day but server is still
> in recover state.
> >So does it only affect the initial lease time?
> >
> >cheers
> >
> >-----Original Message-----
> >From: dhcp-users-bounces at lists.isc.org
> [mailto:dhcp-users-bounces at lists.isc.org] On Behalf Of Glenn Satchell
> >Sent: Wednesday, 18 March 2009 3:53 p.m.
> >To: dhcp-users at lists.isc.org
> >Subject: Re: dissecting DHCP - Q3
> >
> >
> >>From: "Defryn, Guy" <G.P.Defryn at massey.ac.nz>
> >>To: Users of ISC DHCP <dhcp-users at lists.isc.org>
> >>Date: Wed, 18 Mar 2009 15:42:29 +1300
> >>Subject: dissecting DHCP - Q3
> >>
> >> Once again thanks for the response to previous questions.
> >>
> >> Here is the next one,
> >>
> >> I stopped both my servers and deleted the lease files, created empty lease
> >file
> >> and restarted service.
> >> My client issued a renewal and picked up lease. What I did notice was
> >> That the lease is only valid for 30 minutes.
> >> The lease specified in dhcpd.conf is a day.
> >> Is this 30 minute lease because it was obtained while my servers are in
> >recover state?
> >>
> >> cheers
> >>
> >>
> >>
> >> Guy Defryn
> >
> >Yes, it's the time you set for "mclt" in the failover section of dhcpd.
> >
> >regards,
> >-glenn
> >
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