What port does DNS use?

The Domain Name System (DNS) primarily uses the following ports:

1. UDP Port 53:

   • Primary Use: DNS queries and responses.
   • Details: Most DNS queries are sent over UDP port 53 because UDP is a connectionless protocol that allows for quick, efficient querying with minimal overhead. DNS queries usually fit within a single UDP packet.

2. TCP Port 53:

   • Primary Use: DNS zone transfers and larger DNS responses.
   • Details: While UDP is used for most DNS lookups, TCP port 53 is used for DNS zone transfers between DNS servers (e.g., AXFR and IXFR transfers) and for queries that exceed the size limit of a UDP packet (typically greater than 512 bytes). TCP is used in these cases to ensure reliable and complete data transfer.

In summary, DNS uses UDP port 53 for most of its queries and responses, but it also uses TCP port 53 for tasks that require more reliable data transfer, such as zone transfers and large responses.