[ntp:questions] Re: Peer Statement

Brian Utterback brian.utterback at sun.removeme.com
Fri Oct 21 17:37:12 UTC 2005

DJ wrote:
> Ok. But what about
> ServerA ntp.conf
> server time.windows.com
> ServerB ntp.conf
> peer ServerA
> Then Serverb is trying to peer with ServerA. But ServerA doesn't have a
> peer directive - what happens here ? Also, what's the difference
> between this and ServerC doing ntpdate ServerA ???
> I just don't see what's betweenpeer and ntpdate. (I don't think Server
> B with a peer ServerA 'sends' time to server A  - it will only give
> time to ServerA if serverA asks for it so what's the difference ???)

There are a couple of different types of peer associations, symmetric
active and symmetric passive. In the case you have above, ServerB and
ServerA have asymmetric association, with ServerB being symmetric active
(having sent the request to ServerA) while ServerA is symmetric passive.
This presumes that ServerA and ServerB are authenticated and there is
nothing that prevents them from trusting one another.

So, it is only required that one of the two servers have a peer
configured for the other. Both servers can be active by each configuring
a peer for the other, but this doesn't effect the behavior.

To answer your previous question, the ntpd cannot tell the difference
between a client ntpd and a client ntpdate, except that the ntpdate
request will not be repeated and probably doesn't come from port 123.
However, since it is a client mode and not a peer mode packet, the
server will not mobilize an association in either case.


Remember when SOX compliant meant they were both the same color?
Brian Utterback - OP/N1 RPE, Sun Microsystems, Inc.
Ph:877-259-7345, Em:brian.utterback-at-ess-you-enn-dot-kom

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