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Using NTP to sync a group of linux servers to a common time source

I have 20 or so linux servers and I want to sync all of their clocks to a single NTP server, which is in the same rack and switch as my servers. Nothing is virtualized.




Our admins are having trouble getting the clocks on the various machines synced closer than about 500 ms. I would have guessed, and this post implies that we should be able to get the linux boxes synced to within 2 ms of of the source and each other.



Are my expectations for NTP unreasonable? Any hints as to what the admins should be doing/checking?

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