Why does Cloudflare's DNS not resolve some DuckDNS domains, while Google's does?

I got this today:

C:\Users\me>nslookup box.duckdns.org 1.1.1.1 Server: 1dot1dot1dot1.cloudflare-dns.com Address: 1.1.1.1 *** 1dot1dot1dot1.cloudflare-dns.com can't find box.duckdns.org: Server failed C:\Users\me>nslookup box.duckdns.org 8.8.8.8 Server: google-public-dns-a.google.com Address: 8.8.8.8 Non-authoritative answer: Name: box.duckdns.org Address: 86.178.64.217 

I would expect these two nameserver to return the same answer, yet they don't. Is that a problem on Cloudflare's DNS service, or do I misunderstand anything?

I should add that other domains resolve fine on both DNS servers.

1 Answer

Why does Cloudflare's DNS not resolve some DuckDNS domains, while Google's does?

Because CloudFlare had some needs to change it.(Technical issue, DDoS, mistake...)
BTW, I had similar issue with Google's public DNS. It shouldn't be for a long time, usually it is an issue in DNS propagation when some name server doing upgrade, mistake and so on... Both Google and CloudFlare public DNS are forwarding servers that gather information from name servers that are responsible for some particular zone.

Instead of using hard-coded IP address you better have to use in such cases one of official name servers that serves duckdns.org zone, which are:

ns1.duckdns.org ns2.duckdns.org ns3.duckdns.org 

nslookup box.duckdns.org ns2.duckdns.org

I suggest to switch temporary your system wide DNS either to 8.8.8.8 until propagation/misconfiguration issue wouldn't be resolved at CloudFlare or use your ISP provider's DNS or simply use gateway/router IP that must automatically use ISP's DNS if you are on DHCP.