I'm experiencing symptoms similar to those of the other question. That is, peoples are complaining about a domain name being inaccessible. And then, it suddenly starts working after a while. But I doubt it's because of unreliable
DNS servers. They are of my domain name registrar, which is pretty popular in my country.
Could there be some other reasons for this? It's a subdomain, like in
sub.example.com and I make it work with wildcard
DNS record. Could that possibly be a reason? Maybe some old
DNS servers doesn't understand these sort of things? The other reason I can think of is some temporary issues in the internet, like some hosts can't access the other ones? Or some
DNS servers filtering out records by some criterion?
UPD The setup is simple, no load balancers, no clusters, no round-robin
DNS servers. And I'm talking about publicly available server. The users are the users of the internet. I'm managing both
sub.example.com. They are in one
UPD Or maybe after all it's because of the domain registrar. Its servers respond with a timeout:
>nslookup sub.example.com ns.domain.registrar.com DNS request timed out. timeout was 2 seconds. Server: UnKnown Address: 188.8.131.52 Name: sub.example.com Address: 184.108.40.206
I suppose, not all the DNS-servers would tolerate timeouts, don't you think?