Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Optionsfor DHCPv6

Danny Mayer <mayer@ntp.org> Mon, 26 November 2007 03:00 UTC

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Date: Sun, 25 Nov 2007 21:57:12 -0500
From: Danny Mayer <mayer@ntp.org>
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To: Mark Andrews <Mark_Andrews@isc.org>
Subject: Re: [ntpwg] [dhcwg] Re: Network Time Protocol (NTP) Optionsfor DHCPv6
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Cc: ntpwg@lists.ntp.org, dhcwg@ietf.org, Brian Utterback <brian.utterback@sun.com>, Ted Lemon <mellon@fugue.com>, "Richard Gayraud (rgayraud)" <rgayraud@cisco.com>
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Mark Andrews wrote:
>> On Nov 25, 2007, at 3:24 PM, Brian Utterback wrote:
>>> If a client is served an IP address at start up time, it has no  
>>> choice but to use that address for the
>>> entire time it is up and running.
>> This is simply not true.   The client would get the currently- 
>> configured NTP server IP address every time it renews its lease.    
>> It's true that some NTP clients may not bother to check their  
>> configuration information for updates, but it is not true that they  
>> have no choice - checking for configuration updates is trivial.
>>
>> Indeed, I would say that at this late date, a network service that  
>> gets its configuration information from the DHCP client, but does not  
>> follow updates to that information, is broken.  Information provided  
>> by the local DHCP server will most likely change when the client moves  
>> from network to network.   The information that worked on one network  
>> may not work at all on another.   This is true whether the information  
>> is a domain name or an IP address.
> 
> I would think that this should be a push operation from the dhcp
> client rather than a pull operation.  A trivial push would be for
> the DHCP client to re-start the NTP client on address change (NTP
> server and optionally lease address change).
> 
> I already do the later as the NTP client doesn't notice lease address
> changes.
> 
> Mark

You must be running an old NTP server. As of 4.2.4 ntpd rescans the
interfaces for local interface address changes. You can disable
rescanning by using -U 0 on the startup command line.

Danny

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