FYI: Ipv6 users should use 2.pool.ntp.org as their NTP server

[IsaacFL]

For those who have ipv6 and want to use pool.ntp.org as the time server for your NTP clients, they should use 2.pool.ntp.org as this is the only one that returns both A and AAAA records for NTP servers. pool.ntp.org is ipv4 only and many people by default use pool.ntp.org

This also works for regional servers. i.e I am in the US so I use 2.us.pool.ntp.org. It also works for the distro specific entries like 2.pfsense.pool.ntp.org and 2.fedora.pool.ntp.org. Only 2 returns v6 entries.

[Sergei_Shablovsky]

@isaacfl What is situation on Apr 2023 with this?

I mean is there are new NTP pools with AAAA added, or old reconfigured ?

And another question how You check ability of servers/pools to correctly working with ipv6 clients?

Thanks!

[johnpoz]

@sergei_shablovsky I think 2.xxxx the only pools that have AAAA entries..

Be it country, or zone based like north-america or africa, asia, etc.. Or vendor specific like 2.pfsense.ntp

NTP suggests that if your a vendor that will be setting up ntp on the devices you sell/distribute that you register your own vendor name for the zones, etc. Lets say it is stronger than a suggestion ;)

"You must absolutely not use the default pool.ntp.org zone names as the default configuration in your application or appliance. "

Now what a user changes ntp to use after they set it up, would not be the vendors problem - but ntp is pretty against vendors shipping their stuff with the default pool names..

https://www.ntppool.org/en/vendors.html

But I believe only ones that start with 2 have IPv6, all the other 0, 1 and 3 only have IPv4

[maverickws]

I use time.apple.com and time.euro.apple.com both pools and IPv6 enabled for idk maybe over a decade?

[compuguy]

You can add time.nist.gov as a ntp host/pool that returns a AAAA record to the list as well.

[RobbieTT]

The 'teaching' back in the day was to use real v4 or v6 addresses as part of the mix to ensure that a DNS failure would not interrupt NTP.

The NTP pools discouraged that these days but old habits and logic die hard.

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[JKnott]

I use 3 stratum 1 servers from a local Internet exchange, along with 2 stratum 2 from the Canadian government and time.google.com. The 3 Internet exchange servers and Google have both IPv4 and IPv6 addresses available.

The University of Toronto has two NTP servers, tick & tock.

[RobbieTT]

@jknott

I like to have a stratum 1 on the LAN side, as part of the wider mix:

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[JKnott]

@robbiett

Unfortunately, many of us don't have a stratum 0 source. My LAN sees a stratum 2 server.

[darkonc]

@maverickws That's no big surprise. The 2.* rule is for 2.*.pool.ntp.org . Other organizations / domains can do whatever they want.