Vesta Control Panel - Forum

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 was reading an article about allowing TCP on DNS and they seem to have some good points to do so:

• DNSSEC Creates Larger DNS Responses which are over the 512 bytes limit of UDP
• IPv6 DNS Lookups May be Larger Than 512 Bytes, which is the limit of UDP

Maybe consider this information for the next versions?

Taken from here.

You can allow this by opening TCP port 53 on Vesta firewall. Add a new firewall rule and set:
Action: ACCEPT
Protocol: TCP
PORT: 53
IP address: 0.0.0.0/0
Comment: DNS