The Domain Name System (DNS) uses UDP port 53 and TCP port 53. Your storage system does not typically listen on these ports because it does not run a domain name server. However, if DNS is enabled on your storage system, it makes outgoing connections using UDP port 53 for host name and IP address lookups.
The storage system never uses TCP port 53 because this port is used explicitly for communication between DNS servers. Outgoing DNS queries by your storage system are disabled by turning off DNS support. Turning off DNS support protects against receiving bad information from another DNS server.
Because your storage system does not run a domain name server, the name service must be provided by one of the following:
DNS must be enabled for participation in an Active Directory domain.