What is the function of a secondary DNS zone?

• A. A secondary zone stores a writable copy of DNS data.
• B. A secondary zone enables dynamic updates from clients.
• C. A secondary zone is a read-only copy of the primary zone used for redundancy.
• D. A secondary zone is a complete DNS server.

Answer: (C)

In DNS, a secondary zone serves as a backup copy of a zone's data to provide redundancy and reliability. It holds a read-only replica of the primary zone and keeps itself in sync by performing zone transfers from the primary server. Because it’s read-only, clients don’t update it directly—updates go to the primary, and the secondary periodically refreshes to reflect those changes. This setup lets name resolution continue even if the primary server is unavailable, since the secondary can still answer queries for that zone. The other statements don’t fit because a secondary zone is not writable, it isn’t used for dynamic updates, and it isn’t a complete DNS server on its own.