ITGSS Certified Technology Specialist

Which DNS record type is not considered valid?

1. A

2. AAAA

3. CNAME

4. PTR

The correct answer is: PTR

The answer indicating that PTR is not considered a valid DNS record type is incorrect. In fact, PTR records, or Pointer records, are valid and serve a specific purpose in DNS. They are used primarily for reverse DNS lookups, which enable the translation of an IP address back into a domain name. This is particularly useful for various applications, such as verifying the authenticity of a domain when receiving emails or providing additional context for network operations. The other record types listed—A, AAAA, and CNAME—are also valid DNS record types. An A record maps a domain name to an IPv4 address, while an AAAA record maps a domain name to an IPv6 address. CNAME records are used to create aliases for a domain name, allowing multiple domain names to point to the same IP address or server without needing to update each record separately. In summary, each of the record types mentioned serves essential functions within the Domain Name System, and PTR records are indeed valid and serve the critical role of facilitating reverse lookups.