Stefan's blag and stuff

Blog – www.pool.ntp.org and IPv6

The NTP POOL PROJECT is a directory of public usable ntp servers on the internet. In europe (www.pool.ntp.org/zone/europe) there are currently 1892 IPv4 and 707 IPv6 active ntp servers. Since IPv6 is cool, I tried to use one of them. I issued a DNS query for the AAAA record

$ dig AAAA pool.ntp.org

but it doesn't returned an IPv6 address. So I tried

$ dig AAAA 0.pool.ntp.org
$ dig AAAA 0.de.pool.ntp.org
$ dig AAAA 1.de.pool.ntp.org

and finally I used

$ dig AAAA 2.de.pool.ntp.org
;; ANSWER SECTION:
2.de.pool.ntp.org.	115	IN	AAAA	2001:6f8:1ccd::1
2.de.pool.ntp.org.	115	IN	AAAA	2a03:4000:6:107d::1
2.de.pool.ntp.org.	115	IN	AAAA	2001:638:504:2000::32
2.de.pool.ntp.org.	115	IN	AAAA	2001:638:502:137::23

Bingo! Here they are.

But why does only the third pool contain IPv6 ntp servers? I don't have the real answer but I found the official blogpost Continuing IPv6 deployment. It's from 2011, but it seems to be sill valid.

World IPv6 Day is over, but we'll continue to serve AAAA (IPv6) records for 2.pool.ntp.org (and 2.europe, 2.fedora, 2.debian, etc).

IPv6 servers are only served on the 2.<name>.pool.ntp.org domains.

To use the IPv6 ntp servers you have to add the correct pool to your config file /etc/ntpd.conf. On my gentoo systems using the openntpd ntp server it looks like:

# use a random selection of NTP Pool Time Servers
# see http://support.ntp.org/bin/view/Servers/NTPPoolServers
#servers pool.ntp.org
servers 2.de.pool.ntp.org

If you want to check whether your ntp daemon uses some IPv6 connections, just type the command netstat -up.

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