DNS (Domain Name System) in Computer Networks - Mini Project: Build & Apply

Understanding DNS (Domain Name System)

📖 Scenario: You want to understand how the Domain Name System (DNS) works by creating a simple representation of DNS records and how they map domain names to IP addresses.

🎯 Goal: Build a simple DNS record dictionary, add a query domain, find the IP address for that domain, and complete the lookup process.

📋 What You'll Learn

Create a dictionary with domain names as keys and IP addresses as values

Add a variable for the domain name to query

Write code to find the IP address for the query domain using the dictionary

Complete the lookup by storing the result in a variable

💡 Why This Matters

🌍 Real World

DNS is used every time you visit a website to translate the domain name into an IP address computers understand.

💼 Career

Understanding DNS is important for network administrators, web developers, and IT professionals who manage internet connectivity and website hosting.

1

Create DNS records dictionary

Create a dictionary called dns_records with these exact entries: 'example.com': '93.184.216.34', 'openai.com': '104.18.30.162', and 'github.com': '140.82.114.4'.

Computer Networks

# Create the dns_records dictionary with domain-IP pairs
# Your code here

Hint

Use curly braces {} to create a dictionary with domain names as keys and IP addresses as values.

2

Add query domain variable

Create a variable called query_domain and set it to the string 'openai.com'.

Computer Networks

dns_records = {
    'example.com': '93.184.216.34',
    'openai.com': '104.18.30.162',
    'github.com': '140.82.114.4'
}
# Create the query_domain variable with the domain to look up
# Your code here

Hint

Assign the domain name you want to look up to the variable query_domain.

3

Lookup IP address for query domain

Create a variable called ip_address and set it to the value from dns_records for the key query_domain.

Computer Networks

dns_records = {
    'example.com': '93.184.216.34',
    'openai.com': '104.18.30.162',
    'github.com': '140.82.114.4'
}

query_domain = 'openai.com'
# Get the IP address for the query_domain from dns_records
# Your code here

Hint

Use the dictionary key access syntax dns_records[query_domain] to get the IP address.

4

Complete DNS lookup process

Create a variable called lookup_result and set it to a string that says "The IP address of {query_domain} is {ip_address}" using an f-string.

Computer Networks

dns_records = {
    'example.com': '93.184.216.34',
    'openai.com': '104.18.30.162',
    'github.com': '140.82.114.4'
}

query_domain = 'openai.com'

ip_address = dns_records[query_domain]
# Create lookup_result string using f-string
# Your code here

Hint

Use an f-string to combine the domain and IP address into a readable message.

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