Free secondary DNS services

If you run an authoritative DNS server and serve your own zones you may know about the need to have decent secondary DNS servers, or "slaves", to back you up. I recently changed mine, followed recommendations by Frankb's page and found new ones.

August 2019 update: so far these are great, so passing the word.

• puck.nether.net: simple, IPv4+IPv6, supports DNSSEC, 1 location; fairly quick to update usually, but had troubles recently (2019-08) so I removed it
• freedns.afraid.org: simple, IPv4, supports DNSSEC, 1 location; a bit slow to update, sometimes times out, but otherwise stable for years
• BuddyNS: fancy, but DNSSEC support is not free, so no
• 1984hosting: simple, IPv4+IPv6, supports DNSSEC, 3 NS; new one I'm trying, so far so good, fast to update