ns3.alpinelinux.org
% whois alpinelinux.org
[…]
Name Server:NS2.ALPINELINUX.ORG
Name Server:NS1.ALPINELINUX.ORG
Name Server:NS3.ALPINELINUX.ORG
[…]
% dig +short -tNS alpinelinux.org @NS1.ALPINELINUX.ORG
ns1.alpinelinux.org.
ns2.alpinelinux.org.
The nameserver ns3 does not respond to dns queries and the other nameservers don’t know it.
(from redmine: issue id 3376, created on 2014-09-23, closed on 2014-11-18)