10 Domain Name System (DNS)

1. Front: What is the primary purpose of the Domain Name System (DNS)?

Back: To translate human-readable fully qualified domain names (like www.professormesser.com) into machine-readable IP addresses.

2. Front: Why is DNS described as a "distributed database"?

Back: Because the DNS database is not stored in one place; it is scattered across thousands of servers located on different networks around the world.

3. Front: What is the role of the root server clusters in the DNS hierarchy?

Back: They are the starting point for DNS queries and direct requests to the appropriate Top-Level Domain (TLD) servers (like .com, .org, .net).

4. Front: What are the two main types of Top-Level Domains (TLDs)?

Back: Generic TLDs (gTLDs) like .com, .org, and Country Code TLDs (ccTLDs) like .us, .ca, .uk.

5. Front: What is the function of an A Record and an AAAA Record?

Back: An A Record maps a hostname to an IPv4 address. An AAAA Record (Quad A) maps a hostname to an IPv6 address.

6. Front: What is a CNAME Record (Canonical Name), and what is its main administrative benefit?

Back: It creates an alias for a hostname (e.g., www.example.com points to mail.example.com). The benefit is that if the IP address of the main server (mail) changes, you only need to update its A Record, and all the CNAMEs will automatically follow.

7. Front: What is the critical function of an MX Record (Mail Exchanger)?

Back: It specifies the mail server responsible for receiving email messages for a domain. Other email servers query the MX record to know where to deliver email.

8. Front: What kind of information is stored in a TXT Record?

Back: Human-readable text, often used for verification, security, and policy information, such as SPF, DKIM, and DMARC records.

9. Front: What is the purpose of an SPF Record (Sender Policy Framework)?

Back: It lists the IP addresses of authorized email servers allowed to send email on behalf of a domain. Receiving servers check it to help detect email spoofing.

10. Front: How does a DKIM Record (DomainKeys Identified Mail) help verify an email's authenticity?

Back: It contains a public key. The sending server signs emails with a private key, and the receiving server uses the public key in the DKIM record to verify the digital signature, proving the email wasn't tampered with and came from an authorized source.

11. Front: What does a DMARC Record (Domain-based Message Authentication, Reporting & Conformance) allow a domain owner to do?

Back: It tells receiving email servers what to do with messages that fail SPF or DKIM checks (e.g., quarantine, reject) and specifies an email address to send reports about those failures.

12. Front: What are the two command-line tools mentioned for querying DNS information?

Back: dig (common on Linux/macOS) and nslookup (common on Windows).

13. Front: What does the TTL (Time to Live) value in a DNS record indicate?

Back: How long (in seconds) a caching DNS server or client should remember the record before it expires and a new query must be made. A low TLL allows for faster changes to propagate.

14. Front: Why is it important to be cautious when making changes to a DNS server's configuration?

Back: Because a single mistake (like an incorrect IP address in an A record) can make a service (like a website or email) completely inaccessible to users on the internet.