We have two DNS servers listed in our NS record. Last night, one of our DNS servers went down. As expected, some DNS servers were not resolving our hostnames. I assumed this would be temporary and would start working once the TTL of our NS records would expire (1 hour).
An hour+ later, I was still getting DNS timeouts from desktops that were using Earthlink, Verizon and OpenDNS severs. I tested to see if the other DNS server was answering:
dig @ns2.example.com www.example.com +short
This worked.
My questions:
- Does anyone have an answer as to why other DNS servers were not hitting our other DNS server even after the TTL expired?
- Do DNS servers prefer a domain's main DNS server (from the
SOA
record)? - Is there any algorithm used to pick a nameserver from the available NS records? I'm assuming this is implementation specific but perhaps there are some standards that apply here.