[ntp:questions] Issues with w32tm on AD network

Danny Mayer mayer at ntp.isc.org
Wed Feb 27 13:41:44 UTC 2008

Martin Burnicki wrote:
> Danny Mayer wrote:
>> Martin Burnicki wrote:
>>> Though it's normally preferable to run ntpd rather than w32time, there is
>>> a limitation if you run ntpd on a domain controller:
>>> The domain members (workstations) will stop detecting the domain
>>> controller automatically as their primary time source, so you'll have to
>>> configure the domain controller explicitely as times source on every
>>> client.
>> Really? Why would it do that? Is this documented somewhere?
> We have tried it with a small test setup and found that w32time domain
> members did identify their PDC as time source when w32time was running on
> the PDC, but not when ntpd was running on the PDC.
> I have recently received a note from someone who seemed to be very familiar
> with Active Directory. That person told me whn w32time starts it makes an
> entry in the LDAP directory which tells the clients at logon that this
> server is also their time server.

I tried running w32time on my domain controller at home and saw nothing 
in the DNS records which is where I would have expected to put such 
information, specifically an SRV record.

The only other possibility that I can think of is by looking at the 
Active Directory LDAP tree which I didn't have time to look at, 
particularly as I would need to know where to look. I find it harder to 
believe that they would put information there but you never know.

> I assume if ntpd would do the same thing then domain clients would also
> detect and accept ntpd running on the PDC.
> Unfortunately I don't have the original note handy right now, so I'll have
> to investigate.
> Martin

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