[ntp:questions] ntpd behavior with multiple pool definitions
rbthomas at cs.rutgers.edu
Fri Jun 16 23:29:23 UTC 2017
tos minclock 7 minsane 5
with two “pool” directives: one for inside my firewall, one for outside.
The inside pool has three members (all stratum 2, all served by the same stratum 1).
The outside pool is
pool us.pool.ntp.org burst preempt
which returns four hosts randomly chosen out of a large pool. The particular group of four seems to be a slowly varying function of time. If I do two “host us.pool.ntp.org” commands in rapid succession, I get the same 4 hosts. If I wait an hour, I will get a different set of four.
The “minsane” clause tells ntpd that it needs at least 5 servers that make it through the selection process to consider itself properly synchronized. It ensures that I have at least two, and usually four, outside servers to fall back on if my single local stratum 1 should go wacky, taking the stratum 2s along with it.
This works quite well for me.
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