Regarding the dhcp lease time

[Sten Carlsen]

Interesting.

Seems the server hands out a lease covering the time from the client's
time to the current server time, essentially forever.

This might have been done to compensate for the elapsed time from the
client sends the request until it is handled.

One might think a cap on that time gap would be appropriate.

I wonder if the client was ahead of the server time wise, would the
lease then be shorter -> negative -> no lease time?

On 06/05/2019 16.54, Murali Krishna wrote:
> Hi,
>
> Before we tried to collect the packet captures. I would like to share
> some information on the issue.
> While analyzing the logs, it has been observed that the system time is
> updated to very old time stamp(almost 5yrs back). From this point
> onwards we are able to see that the huge lease value is getting
> updated in the client lease file. 
>
> 30566:Tue Apr 30 14:58:03 IST 2019
>
> 30804:Tue Apr 30 14:58:24 IST 2019
>
> 31042:Fri May  2 00:00:14 IST 2014
>
> 31280:Fri May  2 00:00:35 IST 2014
>
> 31531:Fri May  2 00:00:56 IST 2014
>
> …
>
> 33379:Fri May  2 00:03:23 IST 2014
>
> 33643:Fri May  2 00:03:44 IST 2014
>
> 33907:Fri May  2 00:04:05 IST 2014
>
> 34171:Fri May  2 00:04:26 IST 2014
>
> 34435:Fri May  2 00:04:47 IST 2014
>
> 34699:Tue Apr 30 15:03:39 IST 2019
>
> 34963:Tue Apr 30 15:04:00 IST 2019
>
>
> Even though the system time is updated to the current time, there was
> no update to the client lease file.  client lease file is updated to
> the correct value only after we restarted the client.
>
>
> Thanks & Regards,
>
> Muralikrishna CH
>
>
> On Tue, Apr 16, 2019 at 10:32 PM Simon Hobson <dhcp1 at thehobsons.co.uk
> <mailto:dhcp1 at thehobsons.co.uk>> wrote:
>
>     Sten Carlsen <stenc at s-carlsen.dk <mailto:stenc at s-carlsen.dk>> wrote:
>
>     > The server is configured with two times, max-lease-time and
>     default-lease-time.
>
>     Just to expend on that ...
>     There is also min-lease-time.
>
>     If the client specifies a desired lease time then the server will
>     give that subject to min and max lease times.
>     If the client does not ask for a specific lease time, then the
>     default lease time is offered.
>
>     As already mentioned, the first thing to do is look more closely
>     at your packet captures. Check which devices the packets come
>     from, and what's in them - particularly what options the client sends.
>
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>
>
>
> -- 
>
>
>
>
> Thanks & Regards,
> Muralikrishna CH
>
>
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