DNS Record Types

Which of the following statements is TRUE regarding a CNAME (Canonical Name) record in DNS?

A) It maps a hostname directly to an IPv4 address.
B) It maps a hostname directly to an IPv6 address.
C) It acts as a DNS shortcut that maps one hostname to another existing hostname.
D) It is used exclusively to route internet email to the correct mail server.
E) It stores arbitrary text data to prove domain ownership to third parties.
F) It delegates authority from a top-level domain registry to AWS Route 53.

Correct Answer: C - It acts as a DNS shortcut that maps one hostname to another existing hostname.

As an AWS administrator, what is the exact architectural difference between an A record and an AAAA record?

A) An A record maps an IP to a hostname; an AAAA record maps a hostname to an IP.
B) An A record maps a hostname to an IPv4 address; an AAAA record maps a hostname to an IPv6 address.
C) An A record delegates a subdomain; an AAAA record maps a MAC address.
D) An A record maps a hostname to an IPv6 address; an AAAA record maps a hostname to an IPv4 address.
E) An A record is an authoritative answer; an AAAA record is a non-authoritative cached answer.
F) There is no technical difference; they are just used by different operating systems.

Correct Answer: B - An A record maps a hostname to an IPv4 address; an AAAA record maps a hostname to an IPv6 address.

You are adding your corporate domain to Office 365. Microsoft asks you to add a specific random text string (e.g., "ms=12345") to your DNS. Which DNS record type is specifically designed for this ownership verification process?

A) CNAME Record
B) MX Record
C) NS Record
D) AAAA Record
E) TXT Record
F) PTR Record

Correct Answer: E - TXT Record

Your email server queries google.com and receives two MX (Mail Exchange) records. Record 1 has a priority of 10, and Record 2 has a priority of 20. How will the email server route the email?

A) It will use Record 2 first because a higher number equals higher priority.
B) It will use Record 1 first because a lower number indicates a higher priority.
C) It will load balance the emails equally between Record 1 and Record 2.
D) It will drop the email because having two MX records creates a routing loop.
E) It will use Record 1 for IPv4 traffic and Record 2 for IPv6 traffic.
F) It will query the TXT record to determine the actual priority sequence.

Correct Answer: B - It will use Record 1 first because a lower number indicates a higher priority.

In the context of the global DNS architecture, what is the primary function of Name Server (NS) records?

A) They map human-readable hostnames to physical IPv4 addresses.
B) They allow for the end-to-end delegation of a DNS zone (e.g., from a TLD to AWS Managed Servers).
C) They determine the routing priority for incoming internet emails.
D) They dictate how long a DNS resolver should cache a record before querying again.
E) They prevent spam by validating the sender's IP address against the domain.
F) They act as a shortcut to map one hostname to another existing hostname.

Correct Answer: B - They allow for the end-to-end delegation of a DNS zone (e.g., from a TLD to AWS Managed Servers).

What is true regarding the impact of setting a HIGH Time To Live (TTL) value on your DNS records? (Choose two)

A) It reduces the overall number of queries hitting your authoritative name servers.
B) It ensures that if you change your server's IP, the update propagates globally within milliseconds.
C) It forces client resolvers to bypass their local cache and perform an authoritative query every time.
D) If you change a server IP, it will take a long time for the world to see the update, potentially causing downtime.
E) It increases the administrative overhead because you have to manually clear the cache of every internet user.
F) It automatically provisions failover A records in case your primary EC2 instance crashes.

Correct Answers: A, D - It reduces the overall number of queries hitting your authoritative name servers., If you change a server IP, it will take a long time for the world to see the update, potentially causing downtime.

You are planning to migrate your production web application to a new AWS server with a different IP address this weekend. What is the recommended best practice regarding DNS TTL?

A) Increase the TTL to its maximum value immediately before the migration to cache the new IP.
B) Temporarily lower the TTL a few days before the migration to prevent caching issues during the switch.
C) Change all A records to CNAME records during the migration window.
D) Delete the NS records temporarily to flush the global DNS cache.
E) Leave the TTL as is, but delete the TXT records to force an authoritative update.
F) Create duplicate A records with both the old and new IP addresses to load balance traffic indefinitely.

Correct Answer: B - Temporarily lower the TTL a few days before the migration to prevent caching issues during the switch.

When a client device performs a DNS query, what makes the response a "Non-Authoritative Answer"?

A) The answer is provided directly by the Root server.
B) The answer lacks an active SSL/TLS certificate.
C) The answer is provided instantly from a resolver's cache rather than querying the source servers.
D) The answer is missing the TXT ownership verification string.
E) The answer contains an IPv6 address instead of an IPv4 address.
F) The answer is provided by a CNAME record instead of an A record.

Correct Answer: C - The answer is provided instantly from a resolver's cache rather than querying the source servers.

You are configuring DNS for a new web server. You create an A record pointing server.company.com to 192.168.1.50. You now want www.company.com to resolve to the same server. Which configuration is considered an architectural ERROR?

A) Creating a second A record pointing www.company.com to 192.168.1.50.
B) Creating a CNAME record pointing www.company.com to server.company.com.
C) Creating a CNAME record pointing www.company.com directly to the IP address 192.168.1.50.
D) Creating a TXT record to prove ownership before creating the A record.
E) Setting the TTL of the new record to 300 seconds.
F) Registering the domain through AWS Route 53.

Correct Answer: C - Creating a CNAME record pointing www.company.com directly to the IP address 192.168.1.50.

Which of the following elements is NOT a required component or function of an MX (Mail Exchange) record?

A) A priority value (e.g., 10, 20) to determine the routing order.
B) A host value pointing to a mail server in the same DNS zone.
C) A host value pointing to an external FQDN (like Office 365).
D) Direct mapping of the mail server's hostname to an IPv6 address.
E) A mechanism to provide failover if the primary mail server goes down.
F) Use by sending email servers to determine the next hop destination.

Correct Answer: D - Direct mapping of the mail server's hostname to an IPv6 addre