Which statement best describes zone transfers?

• A. They replicate the whole DNS data from a secondary to a primary server.
• B. Zone transfers copy zone data from a primary to a secondary server.
• C. Zone transfers change the authoritative server for a zone.
• D. Zone transfers update the DNS resolver cache at clients.

Answer: (B)

Zone transfers are the mechanism by which a DNS zone’s data is copied from the primary (master) server to a secondary (slave) server to keep both servers in sync. This replication ensures the secondary holds the current records so it can answer queries if the primary is down, and it can do this efficiently either as a full transfer or as incremental updates since the last transfer. It does not change which server is authoritative for the zone, and it does not push updates to individual clients’ resolver caches—the caches update as clients query and receive responses.