[ntp:questions] Re: "Proper" way to test simple, new NTP configuration?

Richard B. Gilbert rgilbert88 at comcast.net
Fri May 20 17:55:49 UTC 2005

ohaya wrote:

>I'm trying to setup NTP on a small network consisting of all Sun Solaris
>I'm appending a post that I just made to the Sun admin NG about our
>configuration, but after doing more reading, I'm wondering if maybe the
>problem was 'how' we did the test.
>As mentioned below, to test this, after getting all of the xntpd's up, I
>simply set the clock back on Solaris1, then watched.  Since making the
>post, I've found a couple of msgs that seem to indicate that maybe I
>should have killed the xntpd on Solaris1 (our NTP "server"), then set
>the time back on that system, then restart the xntpd.
>Can someone here comment on this?  What is the best (and easiest way) to
>determine if this simple NTP setup is actually working?
>================= Post about our configuration
>I have a very small network consisting of 4 Solaris servers (Solaris1,
>..., Solaris4) and want to configure NTP so that Solaris2, Solaris3, and
>Solaris4 synch their time to Solaris1.
>This is an isolated network (no outside connection available), so from
>what I've read, I think that Solaris1 should be synched to itself?
>We tried to set this up yesterday, and got the xnptd running on all 4
>machines, but when we tested, it didn't seem that anything was happening
>(we ran snoops on port 123 on several of the machines).
>We tested by first using ntpdate on Solaris2, 3, and 4 to get them
>synched to Solaris1, then starting the xnptd on those machines, then
>setting the system clock on Solaris1 back about 10 minutes, and then
>watching the snoop output for awhile.
>Can someone provide what the basic ntp.conf file should look like for
>Solaris1 and for the other Solaris machines (Solaris2, 3, and 4)?
Don't expect too much from this configuration!!!   A typical, 
undisciplined, computer clock is not a good synchronization source.

The  machine that keeps the best time by itself; e.g. the clock that 
gains or loses the least amount of time, should be selected as the master.

On the master, /etc/ntp.conf should contain the statements
# Declare the local clock to be the clock of last resort.
# It will be used to serve time in the absence of any other.
server              # Local clock, unit 0
fudge stratum 10

On the clients, /etc/ntp.conf  should include:
server <ip address of server>

As I said, don't expect too much.   The server will drift and the 
clients will follow it as best they can.  (Imagine following a drunk 

If you want something that both keeps the correct time and keeps tight 
synchronization, get a hardware reference clock for your server.   A GPS 
timing receiver is generally the best choice if you can site the antenna 
where it has an unobstructed view of the sky.  These can generally be 
had for less than $500 US, a lot less if you get the bare bones (naked 
circuit board, wall wart, hockey puck antenna)!  If not, HF receivers 
for WWV, WWVH, CHU, JJY etc can be used.  VLF receivers (WWVB, MSF, or 
DCF77, etc) are also an option. 

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