ntp servers

[Glenn Satchell]

On Tue, October 8, 2013 6:11 am, Doug Barton wrote:
> On 10/07/2013 12:07 PM, Gary Johnson wrote:
>> On 2013-10-07, Steven Carr wrote:
>>
>>> On 7 October 2013 01:01, Julie Xu <xll40 at hotmail.com> wrote:
>>
>>>> what is default for option ntp-servers? option 4 ? 42 ? or both?
>>
>>> NTP is option 42, option 4 is for the older time protocol.
>>>
>>> But the DHCP clients need to be configured to request/use that option.
>>> This is usually the case on Linux, but on Windows if the client is a
>>> member of Active Directory it will use the Domain Controller for time
>>> sync. Supposedly if a Windows machine is not a member of AD it will
>>> use option 42, but I've never seen that work. From what I've seen on
>>> OS X setting NTP via DHCP isn't supported.
>>
>> I believe NTP is 56.  42 is the TZDB Timezone option, and 41 is the
>> POSIX Timezone option.
>
> There is no need to guess :)
>
>
> https://www.iana.org/assignments/bootp-dhcp-parameters/bootp-dhcp-parameters.xhtml#options

That's a very useful list, but there is no need to even know that. dhcpd
already knows which option to use. See dhcp-options man page:

     option ntp-servers ip-address [, ip-address... ];

       This option specifies a list of  IP  addresses  indicating
       NTP  (RFC  1035) servers available to the client.  Servers
       should be listed in order of preference.

regards,
-glenn