I'm the process of setting up a monitoring of DNS servers of several large web hosts. My goal is to compare their dns servers response times by tracking their response to ping.
In the process, I discovered that Bluehost nameservers do not respond to ping. I tried to get more information by running Pingdom DNS Check on bluehost.com and it produced the following error:
Name server ns1.bluehost.com (18.104.22.168) does not answer queries over TCP.
The name server failed to answer queries sent over TCP. This is probably due to the name server not correctly set up or due to misconfgured filtering in a firewall. It is a rather common misconception that DNS does not need TCP unless they provide zone transfers - perhaps the name server administrator is not aware that TCP usually is a requirement.
I would like to know the following:
- To what extent is the above statement true?
- What are the implications of a nameserver not answering queries over TCP?