DNS Configuration

Question 1

What does DNS stand for?

Answer 1

Domain Name System

Question 2

What is the main purpose of DNS?

Answer 2

Convert domain names (like google.com) to IP addresses

Question 3

How many root server clusters are there in DNS?

Answer 3

13 (but over 1,000 physical servers)

Question 4

What are GTLDs?

Answer 4

Generic Top-Level Domains (like .com, .org, .net)

Question 5

What are country code top-level domains?

Answer 5

Two-letter codes for countries (like .us, .ca, .uk)

Question 6

What is a fully qualified domain name (FQDN)?

Answer 6

A complete domain name (e.g., www.professormesser.com)

Question 7

What is a DNS hierarchy?

Answer 7

The tree-like structure of domain names and subdomains

Question 8

What command can you use on Linux/macOS to query DNS?

Answer 8

dig

Question 9

What command can you use on Windows to query DNS?

Answer 9

nslookup

Question 10

What are DNS resource records?

Answer 10

Entries in the DNS database (like A, AAAA, MX, CNAME)

Question 11

What is an A record?

Answer 11

Maps a domain name to an IPv4 address

Question 12

What is a AAAA record?

Answer 12

Maps a domain name to an IPv6 address

Question 13

What is a CNAME record?

Answer 13

Creates an alias (nickname) for another domain name

Question 14

What is an MX record?

Answer 14

Specifies mail servers for a domain (for email delivery)

Question 15

What is a TXT record?

Answer 15

Stores text information (often used for verification or security)

Question 16

What is the purpose of the TTL in a DNS record?

Answer 16

Determines how long a record is cached before it must be refreshed

Question 17

What is SPF?

Answer 17

Sender Policy Framework (a TXT record to prevent email spoofing)

Question 18

What is DKIM?

Answer 18

DomainKeys Identified Mail (a TXT record for email authentication)

Question 19

What is DMARC?

Answer 19

Domain-based Message Authentication, Reporting & Conformance (a TXT record for email policy)

Question 20

What is a DNS cache?

Answer 20

A temporary storage of DNS records to speed up future requests

Question 21

Why is it important to back up DNS configurations?

Answer 21

To quickly restore service if a mistake is made

Question 22

DNS only converts domain names to IP addresses.

Answer 22

False (DNS also does reverse lookups, email routing, and more)

Question 23

There are exactly 13 root DNS servers in the world.

Answer 23

False (There are 13 root server clusters, but over 1,000 physical servers)

Question 24

A CNAME record points directly to an IP address.

Answer 24

False (CNAME points to another domain name, not an IP)

Question 25

MX records are used for email delivery.

Answer 25

True

Question 26

TXT records can only be used for email verification.

Answer 26

False (TXT records can store any text, including security policies)

Question 27

SPF helps prevent email spoofing.

Answer 27

True

Question 28

DKIM uses a public key stored in a TXT record.

Answer 28

True

Question 29

DMARC tells receiving email servers what to do with failed SPF/DKIM emails.

Answer 29

True

Question 30

The dig command is only available on Linux.

Answer 30

False (dig is also available on macOS and can be installed on Windows)

Question 31

nslookup can only query A records.

Answer 31

False (nslookup can query any DNS record type)

Question 32

DNS is a centralized database.

Answer 32

False (DNS is a distributed database)

Question 33

A shorter TTL means DNS changes propagate faster.

Answer 33

True

Question 34

DNS records never expire.

Answer 34

False (DNS records expire based on their TTL)

Question 35

A user types "professormesser.com" into their browser. What DNS record type is used to find the IP address?

Answer 35

A or AAAA record

Question 36

A company wants to ensure email from their domain is not marked as spam. What DNS records should they configure?

Answer 36

SPF, DKIM, and DMARC

Question 37

A website is down because its IP address changed, but users still see the old IP. What DNS setting needs to be adjusted?

Answer 37

TTL (Time to Live)

Question 38

An administrator wants to create an alias for "mail.example.com" called "smtp.example.com". What DNS record type should they use?

Answer 38

CNAME

Question 39

A company wants to receive email at "contact@example.com". What DNS record type must be configured?

Answer 39

MX record

Question 40

A user wants to verify ownership of their domain for a third-party service. What DNS record type is often used for verification?

Answer 40

TXT record

Question 41

A company wants to ensure only authorized servers can send email on their behalf. What DNS record type should they use?

Answer 41

SPF

Question 42

An email server receives a message claiming to be from "professormesser.com". How can it verify the message is legitimate?

Answer 42

Check SPF, DKIM, and DMARC records

Question 43

A DNS administrator wants to test a new IP address for a website without affecting all users. What can they do?

Answer 43

Set a short TTL, update the A record, and monitor

Question 44

A user cannot access a website, but others can. What could be the issue?

Answer 44

Cached DNS record (flush DNS cache or wait for TTL to expire)

Question 45

A company wants to block email spoofing. What DNS records should they implement?

Answer 45

SPF, DKIM, and DMARC

Question 46

A network administrator wants to check the MX records for a domain. What command can they use?

Answer 46

dig MX domain.com or nslookup -type=MX domain.com

Question 47

A website is slow to load after a DNS change. What could be the cause?

Answer 47

High TTL causing old records to be cached

Question 48

A company wants to ensure their email is digitally signed. What DNS record type should they use?

Answer 48

DKIM

Question 49

A user wants to see all TXT records for a domain. What command can they use?

Answer 49

dig TXT domain.com or nslookup -type=TXT domain.com