Which DNS record indicates the Start of Authority for a zone?

• A. A
• B. SOA (Start of Authority)
• C. MX
• D. CNAME

Answer: (B)

In DNS, the Start of Authority exists to mark the authoritative source for a zone. The SOA record is placed at the zone’s apex and defines who is responsible for the zone, the primary name server, and administrative contact, along with metadata like the zone’s serial number and timing parameters (refresh, retry, expire) and negative caching TTL. This record is the formal indicator that the data for that zone is authoritative and where to propagate updates.

Other records have different roles: A maps a hostname to an IPv4 address, MX specifies which mail server handles mail for the domain, and CNAME creates an alias to another canonical name. So, the record that indicates the Start of Authority for a zone is the SOA record.