Regarding the dhcp lease time

Murali Krishna muralikrishch at
Tue May 7 16:58:40 UTC 2019


Shift in the system clock is part of the usecase(got this information from
local team).
Also collected the pcap file by reproducing the issue.   I have taken the
screenshot of the pcap file where it clearly mentions about the huge lease

Im not very sure whether it is ok to attach the complete pcap file to the

Also could you please help me understand how the lease value is calculated?
How the lease value is calculated at the server end and provided to the
client? How the client lease file is updated?

In the current scenario(in one of the execution) where the time stamp is
updated to the older value as part of the use case
Time stamp on the Server is:
date:  date: Fri May 2 00:00:17 IST 2014

Time stamp on the client side is:
date: Tue May 7 15:12:08 IST 2019

>From the lease file(content) on the client side:
  option dhcp-lease-time 158253456;
  option dhcp-message-type 5;
  option dhcp-server-identifier;
  renew 5 2021/06/11 03:34:31;
  rebind 2 2023/09/26 02:07:54;
  expire 0 2024/05/12 01:02:36;

This dhcp-lease-time is matching approximately to the difference in the
timestamps of server and the client.

Many thanks in advance.

Thanks & Regards,
Muralikrishna CH

On Tue, May 7, 2019 at 1:57 AM Simon Hobson <dhcp1 at> wrote:

> Murali Krishna <muralikrishch at> wrote:
> > While analyzing the logs, it has been observed that the system time is
> updated to very old time stamp(almost 5yrs back).
> On the server ? If this is the case, then the DHCP service is not your
> problem. You need to find out what's going on with the system clock - until
> you do that then it's pointless trying to solve other problems.
> On the client ? In this case, then I can only *guess* that the client
> service is seeing the time difference between the system clock and the end
> time/date it has stored, and updating something accordingly.
> It might help if you showed the actual log entries, not just the
> timestamps. In any case, the cause of the clock changing should be the
> focus of your investigations.
> _______________________________________________
> dhcp-users mailing list
> dhcp-users at


Thanks & Regards,
Muralikrishna CH
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