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Does anybody know if Ubuntu's NTP servers are redundant? If I dig them, I get:

;; ANSWER SECTION:     280 IN  A

vs. when I dig

;; ANSWER SECTION:       350 IN  A       350 IN  A       350 IN  A

Would this indicate that might be more reliable?

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up vote 5 down vote accepted

The results you get from is a random selection from 3000 available servers in the network. The pool is constantly monitored, and badly performing systems are removed from the pool when they stop providing reliable time.

Ideally, you would want to use the pool servers from your region, which you can find by drilling down to find the closest selection from from the web site.

I am not sure how Ubuntu handles their NTP server internally, and short of asking them, there is no way to be certain. As a general rule though, you should be using NTP servers that you know to be reliable and are close to you.

In any case, you should always have a couple NTP servers defined, so you can just let the NTP protocol pick the best source of time.

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The NTP pool project does geo-DNS, so simply picking or,, etc. should give you servers in your own country, or failing that, in a nearby country. Use of the "0.", "1.", "2." prefixes produces a disjoint set of servers, so you can be guaranteed you will have multiple upstream sources. – rmalayter Jun 15 '12 at 14:16

If you want redundancy in ntpd, use multiple servers. When using a round-robin DNS record (such as the one for, only one IPv4 or IPv6 server is selected for a 'server' line. Repeating the line 3 times will select 3 different servers from the pool.

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