Regarding the dhcp lease time

[Sten Carlsen]

On 06/05/2019 18.06, Murali Krishna wrote:
> Hi Carlsen,
>
> Time on the client side was not observed. Will try to get the time on
> server and the client when this is observed.
> Is this the expected behaviour of the dhcp that the server hands out a
> lease covering the time from the clients time to the current server time?
I don't know. IIRC time from both ends is in the packets.

I am sure someone else knows how the time is actually calculated, I was
mostly guessing.

Sten
>
> Thanks & Regards,
> Muralikrishna CH
> On Mon, May 6, 2019 at 9:07 PM Sten Carlsen <stenc at s-carlsen.dk
> <mailto:stenc at s-carlsen.dk>> wrote:
>
>     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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>
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>
> -- 
>
>
>
>
> Thanks & Regards,
> Muralikrishna CH
>
>
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