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Today's Topics:
1. Re: Regarding the dhcp lease time (Sten Carlsen)
2. Re: Regarding the dhcp lease time (Bob Harold)
----------------------------------------------------------------------
Message: 1
Date: Mon, 6 May 2019 18:54:19 +0200
From: Sten Carlsen <st...@s-carlsen.dk>
To: dhcp-users@lists.isc.org
Subject: Re: Regarding the dhcp lease time
Message-ID: <bed6d314-7ab8-ac93-c4cf-05108d01d...@s-carlsen.dk>
Content-Type: text/plain; charset="utf-8"
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 <st...@s-carlsen.dk
> <mailto:st...@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
>> <dh...@thehobsons.co.uk <mailto:dh...@thehobsons.co.uk>> wrote:
>>
>> Sten Carlsen <st...@s-carlsen.dk <mailto:st...@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.
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>>
>>
>> --
>>
>>
>>
>>
>> Thanks & Regards,
>> Muralikrishna CH
>>
>>
>> _______________________________________________
>> dhcp-users mailing list
>> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
>> https://lists.isc.org/mailman/listinfo/dhcp-users
>
> _______________________________________________
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> dhcp-users@lists.isc.org <mailto:dhcp-users@lists.isc.org>
> https://lists.isc.org/mailman/listinfo/dhcp-users
>
>
>
> --
>
>
>
>
> Thanks & Regards,
> Muralikrishna CH
>
>
> _______________________________________________
> dhcp-users mailing list
> dhcp-users@lists.isc.org
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Message: 2
Date: Mon, 6 May 2019 13:11:58 -0400
From: Bob Harold <rharo...@umich.edu>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Regarding the dhcp lease time
Message-ID:
<ca+nkc8abdsn7o+_tm9lwad+ek4t7fyxqx4ucsd8t8hxrvs8...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
The times in the DHCP packets should all be relative, so it should not
matter if the client and server clocks differ.
https://tools.ietf.org/html/rfc2131#section-3.3
" As clients and servers may not have synchronized clocks, times are
represented in DHCP messages as relative times, to be interpreted
with respect to the client's local clock."
--
Bob Harold
On Mon, May 6, 2019 at 12:54 PM Sten Carlsen <st...@s-carlsen.dk> wrote:
>
>
> 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 <st...@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 <dh...@thehobsons.co.uk>
>> wrote:
>>
>>> Sten Carlsen <st...@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.
>>>
>>> --
>>
>> Thanks & Regards,
>> Muralikrishna CH
>>
>>
> Thanks & Regards,
> Muralikrishna CH
>
>
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