DNS (Domain Name System) in Computer Networks - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the primary purpose of DNS.

Computer Networks

The main function of DNS is to translate [1] names into IP addresses.

Drag options to blanks, or click blank then click option'

Anumeric

Bdomain

Chardware

Dprotocol

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing domain names with IP addresses

Thinking DNS translates hardware names

DNS converts domain names like example.com into IP addresses computers use to communicate.

2fill in blank

medium

Complete the code to show the DNS record type used for mapping domain names to IP addresses.

Computer Networks

The DNS record type that maps a domain name to an IPv4 address is called an [1] record.

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AA

BTXT

CCNAME

DMX

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing MX which is for mail servers

Choosing CNAME which is for aliases

An A record in DNS links a domain name to its IPv4 address.

3fill in blank

hard

Fix the error in the explanation about DNS caching.

Computer Networks

DNS caching helps reduce [1] by storing previous query results temporarily.

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Abandwidth

Berrors

Clatency

Dsecurity

Attempts:

3 left

💡 Hint

Common Mistakes

Thinking caching reduces errors

Confusing bandwidth with latency

DNS caching reduces latency by avoiding repeated lookups for the same domain.

4fill in blank

hard

Fill both blanks to complete the DNS query process description.

Computer Networks

When a DNS resolver receives a query, it first checks its [1] cache and if not found, it queries the [2] DNS server.

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Alocal

Broot

Cauthoritative

Dglobal

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing authoritative with root server

Thinking global cache is checked first

The resolver checks its local cache first, then queries the root DNS server if needed.

5fill in blank

hard

Fill all three blanks to complete the DNS record comprehension example.

Computer Networks

records = { [1]: [2] for [3] in dns_data if dns_data[[3]]['type'] == 'A' }

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Adomain

Bip_address

Crecord

Drecord['name']

Attempts:

3 left

💡 Hint

Common Mistakes

Using record['name'] as key without defining record

Mixing up keys and values

This comprehension creates a dictionary mapping domain names to IP addresses for A records.

Practice

1. What is the main purpose of the DNS in computer networks?

easy

A. To store website content

B. To translate website names into IP addresses

C. To secure internet connections

D. To speed up internet downloads

Solution

1. Step 1: Understand what DNS stands for

   DNS means Domain Name System, which helps computers find websites.

2. Step 2: Identify DNS function

   DNS translates easy-to-remember website names (like example.com) into IP addresses that computers use to connect.

3. Final Answer:

   To translate website names into IP addresses -> Option B

4. Quick Check:

   DNS translates names to IPs = A [OK]

Hint: DNS matches names to numbers (IP addresses) [OK]

Common Mistakes:

• Thinking DNS stores website content
• Confusing DNS with security protocols
• Believing DNS speeds up downloads

2. Which of the following is the correct format of a DNS record that maps a domain to an IP address?

easy

A. TXT record

B. MX record

C. CNAME record

D. A record

Solution

1. Step 1: Recall DNS record types

   DNS uses different record types for different purposes: A records map domains to IP addresses, MX records handle mail servers, TXT records store text info, and CNAME records alias domains.

2. Step 2: Identify record for IP mapping

   The A record specifically maps a domain name to an IPv4 address.

3. Final Answer:

   A record -> Option D

4. Quick Check:

   A record = IP mapping [OK]

Hint: A record = Address (IP) mapping [OK]

Common Mistakes:

• Confusing MX with IP mapping
• Thinking TXT stores IP addresses
• Mixing CNAME with direct IP mapping

3. If you type www.example.com in your browser, which sequence correctly describes what DNS does?

medium

A. Browser sends IP to DNS server -> DNS returns IP -> Browser connects to IP

B. Browser sends IP to DNS server -> DNS returns domain -> Browser connects to domain

C. Browser sends domain to DNS server -> DNS returns IP -> Browser connects to IP

D. Browser sends domain to DNS server -> DNS returns website content -> Browser displays content

Solution

1. Step 1: Understand DNS query process

   When you enter a domain, the browser asks DNS servers for the IP address of that domain.

2. Step 2: Follow DNS response and connection

   The DNS server replies with the IP address, then the browser uses that IP to connect to the website.

3. Final Answer:

   Browser sends domain to DNS server -> DNS returns IP -> Browser connects to IP -> Option C

4. Quick Check:

   Domain to IP to connect = D [OK]

Hint: DNS translates domain to IP before connecting [OK]

Common Mistakes:

• Thinking DNS returns website content
• Confusing domain and IP roles
• Assuming DNS returns domain from IP

4. A user cannot access a website even though the internet connection is fine. Which DNS-related issue is most likely the cause?

medium

A. Incorrect IP address in DNS record

B. Slow internet speed

C. Browser cache is full

D. Website server is down

Solution

1. Step 1: Analyze the problem context

   The internet connection works, so the problem is not network speed or browser cache.

2. Step 2: Identify DNS issue

   If DNS has an incorrect IP address for the website, the browser cannot find the correct server, causing access failure.

3. Final Answer:

   Incorrect IP address in DNS record -> Option A

4. Quick Check:

   Wrong DNS IP causes access failure = B [OK]

Hint: Wrong IP in DNS stops website loading [OK]

Common Mistakes:

• Blaming slow internet when connection is fine
• Assuming browser cache causes DNS errors
• Confusing server downtime with DNS issues

5. You want to create a DNS entry that points blog.example.com to example.com without assigning a new IP. Which DNS record type should you use?

hard

A. CNAME record

B. A record

C. MX record

D. PTR record

Solution

1. Step 1: Understand DNS record purposes

   A records map domains to IPs, CNAME records alias one domain to another, MX records handle mail, PTR records map IPs to domains.

2. Step 2: Choose record for aliasing

   To point blog.example.com to example.com without a new IP, a CNAME record creates an alias to the main domain.

3. Final Answer:

   CNAME record -> Option A

4. Quick Check:

   Alias domain uses CNAME record = A [OK]

Hint: Use CNAME to alias one domain to another [OK]

Common Mistakes:

• Using A record for alias instead of IP
• Confusing MX with domain aliasing
• Thinking PTR is for forward DNS