What ports need to be open for DNS to operate?

Release found: Red Hat Enterprise Linux 4, 5, 6 and 7.

Problem

You wish to know what ports need to be open for the Domain Name Service (DNS) to function properly.

Solution

DNS uses both the TCP and UDP protocols. Lookups performed by clients primarily (but not exclusively) use UDP - when the response data exceeds 512 bytes, the UDP query may fai...