Which DNS record type is used to hold alternative host names such as blog.example.com or shop.example.com?

• A. A record
• B. MX record
• C. PTR record
• D. CNAME record

Answer: (D)

The concept here is DNS aliasing: using a name that refers to another canonical domain name rather than to an IP directly. A CNAME record is specifically used to create an alias for a hostname, so blog.example.com or shop.example.com can point to another domain name that actually hosts the content. When a resolver looks up the alias, it follows the CNAME to the canonical name and then fetches the A or AAAA record for that canonical name to obtain the IP address. This is different from an A record, which maps a name directly to an IP; MX records designate mail servers; and PTR records map an IP back to a name. Note that a CNAME should point to another domain name, not an IP, and you generally don’t mix other records with the same name that has a CNAME.