Duplicate Servers

Richard Laager rlaager at wiktel.com
Wed Sep 25 10:22:41 UTC 2019

At work, I have two NTP servers. They are part of the pool, with both
IPv4 and IPv6.

Internally, my systems use my NTP servers (marked with prefer) and the
pool to provide additional sources. As is typical, ntpd prefers IPv6
after resolving the hostname.

>From time to time, the pool will serve me my own servers. I think ntpd
automatically deduplicates the sources if I get the IPv6 address.
However, if I get one of my own servers back by IPv4 address, I can end
up with a duplicate source.

I'm not sure how harmful this is. Should I care?

If I should care, any suggestions on what I should do? Is using my
sources plus the pool stupid? If not, maybe we could add some sort of
"blacklist this IP from the pool" feature, which would cover this
scenario plus others?


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