In DNS, which record type is used to alias one domain name to another?

• A. MX
• B. A
• C. CNAME
• D. PTR

Answer: (C)

DNS uses a CNAME record to alias one domain name to another. A CNAME maps an alias hostname to a canonical name, so when a resolver asks for the alias, it is continued to be resolved to the IPs of the target name. The alias itself doesn’t hold an IP address; it’s just another name that points to the real destination. This lets you point multiple domain names to the same site without duplicating A or AAAA records. For example, you can make a name like www.example.com resolve to example.org, and the actual IPs come from example.org’s A/AAAA records.

Other common records serve different purposes: MX specifies where mail for the domain should be delivered; A maps a domain name to an IPv4 address; PTR is used for reverse DNS lookups, mapping an IP back to a domain name. Since CNAME is specifically about aliasing one name to another, these other records don’t provide that aliasing behavior.