IP addresses and domain names in Intro to Computing - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding IP Address Classes

Which of the following IP addresses belongs to a Class B network?

A 224.0.0.1

B 10.0.0.1

C 192.168.1.1

D 172.16.0.1

💡 Hint

Recall that Class B IP addresses have their first octet between 128 and 191.

Class B IP addresses range from 128.0.0.0 to 191.255.255.255. The address 172.16.0.1 falls within this range.

❓ trace

intermediate

Domain Name Resolution Process

Consider the following simplified steps of resolving a domain name to an IP address. Which step happens third?

1. User types a domain name in the browser.
2. Browser checks local cache for IP address.
3. Request sent to recursive DNS server.
4. Recursive server queries root DNS server.

A Browser checks local cache for IP address.

B Request sent to recursive DNS server.

C User types a domain name in the browser.

D Recursive server queries root DNS server.

💡 Hint

Think about the order from user action to external queries.

First, the user types the domain name, then the browser checks its cache. If not found, it sends a request to the recursive DNS server, which is the third step.

❓ Comparison

advanced

Comparing IPv4 and IPv6 Addresses

Which statement correctly compares IPv4 and IPv6 addresses?

A IPv4 addresses are 128 bits long; IPv6 addresses are 32 bits long.

B IPv4 addresses use hexadecimal notation; IPv6 addresses use decimal notation.

C IPv4 addresses are written in four decimal numbers separated by dots; IPv6 addresses use eight groups of hexadecimal numbers separated by colons.

D IPv4 addresses support more unique addresses than IPv6.

💡 Hint

Recall the length and notation style of each IP version.

IPv4 addresses are 32 bits long and written as four decimal numbers separated by dots. IPv6 addresses are 128 bits long and written as eight groups of hexadecimal numbers separated by colons.

❓ identification

advanced

Identifying Valid Domain Names

Which of the following is a valid domain name according to standard rules?

A example.com

B -example.com

C example_site.com

D example..com

💡 Hint

Domain names cannot start with a hyphen or have consecutive dots.

Valid domain names can contain letters, numbers, and hyphens but cannot start or end with a hyphen, nor have consecutive dots. 'example.com' follows these rules.

🚀 Application

expert

Calculating Number of Hosts in a Subnet

You have an IPv4 subnet with the mask 255.255.255.240. How many usable host IP addresses are available in this subnet?

A 14

B 16

C 30

D 32

💡 Hint

Count the number of bits available for hosts and subtract network and broadcast addresses.

The subnet mask 255.255.255.240 corresponds to 28 bits for network and 4 bits for hosts. 2^4 = 16 addresses total. Subtract 2 for network and broadcast addresses, leaving 14 usable hosts.

Practice

1. What is the main purpose of a domain name in internet communication?

easy

A. To assign a unique numeric label to a device

B. To provide an easy-to-remember name linked to an IP address

C. To encrypt data sent over the internet

D. To store website content

Solution

1. Step 1: Understand what domain names represent

   Domain names are human-friendly names that help us remember website addresses instead of numbers.

2. Step 2: Compare domain names with IP addresses

   IP addresses are numeric labels, while domain names are easy names linked to those numbers.

3. Final Answer:

   To provide an easy-to-remember name linked to an IP address -> Option B

4. Quick Check:

   Domain name = Easy-to-remember name [OK]

Hint: Domain names are like website nicknames [OK]

Common Mistakes:

• Confusing domain names with IP addresses
• Thinking domain names encrypt data
• Believing domain names store website content

2. Which of the following is the correct format of an IPv4 address?

easy

A. 192.168.1.1

B. 192-168-1-1

C. 192:168:1:1

D. 192/168/1/1

Solution

1. Step 1: Recall IPv4 address format

   IPv4 addresses consist of four numbers separated by dots, each number between 0 and 255.

2. Step 2: Check each option's format

   Only 192.168.1.1 uses dots as separators and valid numeric ranges.

3. Final Answer:

   192.168.1.1 -> Option A

4. Quick Check:

   IPv4 uses dots between numbers [OK]

Hint: IPv4 addresses use dots, not dashes or colons [OK]

Common Mistakes:

• Using dashes or colons instead of dots
• Confusing IPv4 with IPv6 format
• Using slashes as separators

3. Given the domain name example.com, what does the DNS server do when you type it in your browser?

medium

A. It translates example.com into its IP address

B. It encrypts your browsing data

C. It stores the website files locally

D. It blocks access to the website

Solution

1. Step 1: Understand DNS server role

   DNS servers translate domain names into IP addresses so browsers can find websites.

2. Step 2: Match the action to the options

   Only It translates example.com into its IP address describes this translation process correctly.

3. Final Answer:

   It translates example.com into its IP address -> Option A

4. Quick Check:

   DNS = Domain to IP translation [OK]

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

Common Mistakes:

• Thinking DNS encrypts data
• Believing DNS stores website files
• Assuming DNS blocks websites

4. A user tries to access www.example.com but gets an error. The DNS server is suspected. Which of these is a likely cause?

medium

A. The website files are missing on the server

B. The user's computer has no internet cable connected

C. The browser cache is full

D. The DNS server failed to translate the domain name to an IP address

Solution

1. Step 1: Identify DNS server's role in domain resolution

   If DNS fails, the domain name cannot be converted to an IP address, causing access errors.

2. Step 2: Evaluate other options

   Options A, B, and D relate to other issues, not DNS translation failure.

3. Final Answer:

   The DNS server failed to translate the domain name to an IP address -> Option D

4. Quick Check:

   DNS failure = domain name not resolved [OK]

Hint: DNS failure means no IP address found for domain [OK]

Common Mistakes:

• Confusing DNS failure with physical connection issues
• Blaming browser cache for DNS errors
• Assuming website files missing cause DNS errors

5. You want to block access to a website by modifying the local hosts file. Which entry correctly blocks badwebsite.com by redirecting it to the local machine?

hard

A. 255.255.255.0 badwebsite.com

B. 192.168.1.1 badwebsite.com

C. 127.0.0.1 badwebsite.com

D. 0.0.0.0 badwebsite.com

Solution

1. Step 1: Understand hosts file redirection

   The hosts file maps domain names to IP addresses locally. Redirecting to 127.0.0.1 (localhost) blocks the site.

2. Step 2: Evaluate IP addresses for blocking

   127.0.0.1 is the standard localhost IP; 192.168.1.1 is a private network IP; 255.255.255.0 is a subnet mask; 0.0.0.0 can also block but 127.0.0.1 is more common and reliable.

3. Final Answer:

   127.0.0.1 badwebsite.com -> Option C

4. Quick Check:

   Hosts file redirect to localhost = block site [OK]

Hint: Use 127.0.0.1 to block sites via hosts file [OK]

Common Mistakes:

• Using subnet masks or invalid IPs in hosts file
• Confusing private IPs with localhost
• Using 0.0.0.0 which may not work on all systems