[ntp:questions] A theoretical question

Denis Zaitsev zzz at natasha.ward.six
Thu Nov 6 20:45:05 UTC 2003


There is a small LAN with one Linux machine has a dialup access to the
internet.  And this machine is also a NTP server for the LAN.  It uses
the LOCAL (127.127.1.0) clock.  I want to synchronize this machine
with an external NTP servers thru the PPP sessions.

a) I do this that way: when the PPP link is up, I run ntpdc and
unconfig 127.127.1.0 and config some quantity of the external servers.
When PPP link is down, I do the reverse work.  And it seems that this
method works.

b) There is another way: to config the external servers once and do
not do any swaps.  The NTP server lives happily without the LOCAL
clock, and just complains sometimes when PPP is off about an
unreachability of the external servers.  When PPP is on my NTP server
reestablishes the connections and resets the time, if it is a need.
And again, it seems that it works.

c) And there is the third way: (b) plus LOCAL clock at low priority,
to be used at the absence of an access to the "real" servers.

So, my question is: what are the weakness of each of these methods?
They all seem to work, but I have a paranoid feeling, thet they give
the different results...

Thanks in advance.



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