ITGSS Certified Technology Specialist

Which of the following is not a valid DNS record type?

1. MX

2. TXT

3. A

4. PTR

The correct answer is: MX

The focus of the question is on identifying a type of DNS record that does not exist. DNS, or Domain Name System, is essential for resolving domain names into IP addresses and vice versa. Various record types serve distinct purposes in this system. MX records, for example, are used to specify mail exchange servers responsible for receiving email on behalf of a domain. TXT records allow domain administrators to include arbitrary text strings in the DNS and are often used for verification and policy definitions. A records (Address records) map a domain to its associated IP address, and PTR records (Pointer records) are used for reverse DNS lookups, linking an IP address back to a domain name. In this context, while all the aforementioned options are indeed valid DNS record types used in various applications across the internet, the answer provided mistakenly identifies MX as the invalid one. Consequently, the determination of which is not a valid DNS record would need to review the complete list of DNS record types. Since all presented options are valid, it underscores the importance of familiarizing oneself with the various DNS record types for effective IT operations.