Which DNS record types and purposes are commonly used for domain name resolution and mail routing?

Which DNS record types and purposes are commonly used for domain name resolution and mail routing?

• A. A maps domain to IPv4; AAAA maps to IPv6; CNAME provides an alias to another domain; MX designates mail servers for the domain.
• B. A maps domain to IPv4; AAAA maps to IPv6; CNAME maps to an IP address because it is a direct record; MX maps to web servers.
• C. A maps domain to IPv4; AAAA maps to IPv6; NS stores name servers for the domain; MX maps to web servers.
• D. A maps domain to IPv4; AAAA maps to IPv6; CNAME maps to hostnames; MX designates mail servers.

Answer: (A)

The key idea is how DNS records map names to resources and route mail. A records translate a domain to an IPv4 address, while AAAA records do the same for IPv6. A CNAME record creates an alias from one domain name to another domain name, so requests for the alias are resolved by looking up the canonical name it points to. MX records specify which mail servers handle email for the domain, including their priority. This combination is the most accurate description of common domain resolution and mail routing behavior: A and AAAA provide the actual host addresses, CNAME offers an alias mechanism to another domain, and MX designates the mail servers for the domain. Why the other descriptions don’t fit as well: CNAME pointing directly to an IP address is incorrect because CNAMEs must refer to another domain name, not an IP. Stating that MX maps to web servers mixes mail routing with web hosting, which are separate services. Describing NS as storing name servers is true in delegation terms but doesn’t address mail routing, and the wording about MX mapping to web servers is again inaccurate. The phrasing that CNAME maps to hostnames is true in a broad sense but less precise than describing it as an alias to another domain name.

The key idea is how DNS records map names to resources and route mail. A records translate a domain to an IPv4 address, while AAAA records do the same for IPv6. A CNAME record creates an alias from one domain name to another domain name, so requests for the alias are resolved by looking up the canonical name it points to. MX records specify which mail servers handle email for the domain, including their priority.

This combination is the most accurate description of common domain resolution and mail routing behavior: A and AAAA provide the actual host addresses, CNAME offers an alias mechanism to another domain, and MX designates the mail servers for the domain.

Why the other descriptions don’t fit as well: CNAME pointing directly to an IP address is incorrect because CNAMEs must refer to another domain name, not an IP. Stating that MX maps to web servers mixes mail routing with web hosting, which are separate services. Describing NS as storing name servers is true in delegation terms but doesn’t address mail routing, and the wording about MX mapping to web servers is again inaccurate. The phrasing that CNAME maps to hostnames is true in a broad sense but less precise than describing it as an alias to another domain name.