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Today's Topics:

   1. DHCP client protocol timing affected by NTP time change
      (Klemen Sladic)
   2. Re: Conditional File Include (Eugene Grosbein)
   3. Re: DHCP client protocol timing affected by NTP time change
      (Eugene Grosbein)


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Message: 1
Date: Tue, 8 Aug 2017 13:37:21 +1200
From: Klemen Sladic <gostur...@gmail.com>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: DHCP client protocol timing affected by NTP time change
Message-ID:
        <can6euafqaugovqtpcfro0r-3jdp7v9s1orngc4n1n3c8nmw...@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Hi.

I am experiencing an interesting problem with DHCP client timeouts.
When the system boots up it set its date/time, starts DHCP client and NTP
client.
Only after the DHCP client interface is configured, the NTP client is able
to access
the NTP server.
In my case, when NTP client adjusts the date/time it is set 12 hours back
because
of different time zone.
I have set a short lease time and noted, that from that point on, there is
no renew
requests initiated by the client.

So, I wonder, is it possible that instead of after 15 seconds the client
will try to
renew in 12 hours and 15 seconds since the time has been set 12 hours in the
past?

Example (timeout calculation is just as an example):
1. bootup, system time Aug 8 02:00:00pm
2. start DHCP client acquire IP at Aug 8 02:01:00pm
    calculated renew on Aug 8 02:01:15pm
3. NTP at 02:01:05PM sets system time to Aug 8 02:01:05AM
4. DHCP client waits nearly 12 hours until system time is Aug 8 02:01:15pm
again

I will look at the source code, but just like to ask if someone knows if
this is
how it should behave or maybe I am missing something (configuration etc.).

Thank you very much in advance.

RegK
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Message: 2
Date: Tue, 8 Aug 2017 14:56:48 +0700
From: Eugene Grosbein <eu...@grosbein.net>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: Conditional File Include
Message-ID: <59896ec0.6060...@grosbein.net>
Content-Type: text/plain; charset=windows-1252

08.08.2017 3:23, Simon Hobson wrote:

> Eugene Grosbein <eu...@grosbein.net> wrote:
> 
>> Just put all identical configuration to single included file
>> and include it to two distinct dhcpd.conf's each having own "failover peer"
>> statements and, perhaps, something other like "subnet".
> 
> I suspect the reason is that it moves some of the config outside of the 
> management process.

I don't see how that would occur.

> While it works, it means that the config is now split in 3 places -
> while the aim was to keep it in one place (with tracking of changes etc).

One cannot keep failover configs in one place without some kind of 
preprocessing.

And every part of config is still kept in one of 3 single places,
either in common part or in one of individual parts.

It just works.



------------------------------

Message: 3
Date: Tue, 8 Aug 2017 17:03:28 +0700
From: Eugene Grosbein <eu...@grosbein.net>
To: Users of ISC DHCP <dhcp-users@lists.isc.org>
Subject: Re: DHCP client protocol timing affected by NTP time change
Message-ID: <59898c70.9040...@grosbein.net>
Content-Type: text/plain; charset=windows-1252

08.08.2017 8:37, Klemen Sladic wrote:
> Hi.
> 
> I am experiencing an interesting problem with DHCP client timeouts.
> When the system boots up it set its date/time, starts DHCP client and NTP 
> client.
> Only after the DHCP client interface is configured, the NTP client is able to 
> access
> the NTP server.
> In my case, when NTP client adjusts the date/time it is set 12 hours back 
> because
> of different time zone.

That's plain wrong and that's a root of your problem.
In no way a time zone difference should affect NTP time and kernel time.

The only case it could happen that's client keeping local time in its RTC
instead of UTC time. Fix it to keep UTC time in the RTC and it will be fine.



------------------------------

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