Private vs public IP addresses in Computer Networks - Hands-On Comparison

Understanding Private vs Public IP Addresses

📖 Scenario: You are setting up a small office network and need to understand how devices inside your office communicate with each other and with the internet.

🎯 Goal: Build a simple data structure that lists devices with their IP addresses, identify which IPs are private or public, and mark them accordingly.

📋 What You'll Learn

Create a dictionary with device names as keys and their IP addresses as values.

Add a list of private IP address ranges to check against.

Write logic to determine if each device's IP address is private or public.

Add a final dictionary that shows each device with its IP and whether it is private or public.

💡 Why This Matters

🌍 Real World

Understanding private vs public IP addresses helps in setting up secure home or office networks and managing internet access.

💼 Career

Network administrators and IT support staff need to know how to identify and configure private and public IP addresses for devices.

1

Create the devices dictionary with IP addresses

Create a dictionary called devices with these exact entries: 'Laptop': '192.168.1.10', 'Printer': '10.0.0.5', 'WebServer': '172.16.0.1', 'PublicSite': '8.8.8.8'.

Computer Networks

# Create the devices dictionary with exact IP addresses
# Your code here

Hint

Use a Python dictionary with device names as keys and IP addresses as string values.

2

Add the private IP ranges list

Create a list called private_ranges containing these exact strings: '192.168.', '10.', and '172.16.'.

Computer Networks

devices = {
    'Laptop': '192.168.1.10',
    'Printer': '10.0.0.5',
    'WebServer': '172.16.0.1',
    'PublicSite': '8.8.8.8'
}

# Create the private_ranges list with exact prefixes
# Your code here

Hint

Use a list of strings representing the start of private IP address ranges.

3

Determine if each IP is private or public

Create a dictionary called ip_types that uses a for loop with variables device and ip to iterate over devices.items(). For each IP, check if it starts with any prefix in private_ranges. If yes, set the value to 'Private', otherwise 'Public'.

Computer Networks

devices = {
    'Laptop': '192.168.1.10',
    'Printer': '10.0.0.5',
    'WebServer': '172.16.0.1',
    'PublicSite': '8.8.8.8'
}

private_ranges = ['192.168.', '10.', '172.16.']

# Create ip_types dictionary to mark IPs as 'Private' or 'Public'
# Your code here

Hint

Use a for loop and the startswith() method with any() to check prefixes.

4

Combine devices, IPs, and types into a final dictionary

Create a dictionary called device_info using a dictionary comprehension that iterates over devices.items(). Each key is the device name, and the value is another dictionary with keys 'IP' and 'Type' set to the device's IP and its type from ip_types.

Computer Networks

devices = {
    'Laptop': '192.168.1.10',
    'Printer': '10.0.0.5',
    'WebServer': '172.16.0.1',
    'PublicSite': '8.8.8.8'
}

private_ranges = ['192.168.', '10.', '172.16.']

ip_types = {}
for device, ip in devices.items():
    if any(ip.startswith(prefix) for prefix in private_ranges):
        ip_types[device] = 'Private'
    else:
        ip_types[device] = 'Public'

# Create device_info dictionary with device as key and {'IP': ip, 'Type': type} as value
# Your code here

Hint

Use a dictionary comprehension to combine IP and type info for each device.

Practice

1. Which of the following IP address ranges is reserved for private networks?

easy

A. 192.168.0.0 to 192.168.255.255

B. 8.8.8.8 to 8.8.8.255

C. 172.32.0.0 to 172.47.255.255

D. 1.1.1.1 to 1.1.1.255

Solution

1. Step 1: Identify private IP ranges

   Private IP addresses include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 ranges.

2. Step 2: Match given options to private ranges

   A and B are public ranges. C (172.32.0.0 to 172.47.255.255) is outside the private 172.16.0.0/12 range. D matches the private 192.168.0.0/16 range.

3. Final Answer:

   192.168.0.0 to 192.168.255.255 -> Option A

4. Quick Check:

   Private IP range = 192.168.x.x [OK]

Hint: Private IPs start with 10., 172.16-31., or 192.168. [OK]

Common Mistakes:

• Confusing public IPs like 8.8.8.8 as private
• Not knowing the specific private IP ranges
• Assuming all IPs starting with 1 or 8 are private

2. Which of the following is a valid public IP address?

easy

A. 192.168.1.1

B. 8.8.8.8

C. 172.20.10.5

D. 10.0.0.1

Solution

1. Step 1: Identify private IP addresses

   10.0.0.1, 192.168.1.1, and 172.20.10.5 are all within private IP ranges.

2. Step 2: Check which IP is outside private ranges

   8.8.8.8 is a public IP address used by Google DNS servers.

3. Final Answer:

   8.8.8.8 -> Option B

4. Quick Check:

   Public IP example = 8.8.8.8 [OK]

Hint: Public IPs are not in private ranges like 10., 172.16-31., 192.168. [OK]

Common Mistakes:

• Choosing private IPs as public by mistake
• Not recognizing common public IPs like 8.8.8.8
• Assuming all IPs starting with low numbers are private

3. Consider a device with IP address 192.168.1.10. What type of IP address is this?

medium

A. Loopback IP address

B. Public IP address

C. Broadcast IP address

D. Private IP address

Solution

1. Step 1: Identify the IP address range

   192.168.1.10 falls within the 192.168.0.0 to 192.168.255.255 range, which is reserved for private networks.

2. Step 2: Understand IP address types

   Private IPs are used inside local networks and are not routable on the internet. This matches the given IP.

3. Final Answer:

   Private IP address -> Option D

4. Quick Check:

   192.168.x.x = Private IP [OK]

Hint: 192.168.x.x always means private IP [OK]

Common Mistakes:

• Confusing private IP with public IP
• Thinking 192.168.x.x is loopback or broadcast
• Not knowing IP address classifications

4. A network administrator assigns the IP address 172.32.0.1 to a device. What is the issue with this assignment?

medium

A. 172.32.0.1 is outside the private IP range and should be public

B. 172.32.0.1 is a loopback address and cannot be assigned to devices

C. 172.32.0.1 is a private IP address and cannot be used publicly

D. 172.32.0.1 is a broadcast address and cannot be assigned

Solution

1. Step 1: Check the private IP range for 172.x.x.x

   The private range for 172 is from 172.16.0.0 to 172.31.255.255. The IP 172.32.0.1 is just outside this range.

2. Step 2: Understand implications of IP outside private range

   Since 172.32.0.1 is outside the private range, it is considered a public IP and must be assigned carefully to avoid conflicts.

3. Final Answer:

   172.32.0.1 is outside the private IP range and should be public -> Option A

4. Quick Check:

   172.16-31.x.x = Private, 172.32.x.x = Public [OK]

Hint: 172.16 to 172.31 is private; 172.32 is public [OK]

Common Mistakes:

• Assuming all 172.x.x.x are private
• Confusing broadcast or loopback with this IP
• Not checking exact private IP range boundaries

5. You want to set up a home network that connects multiple devices but does not expose them directly to the internet. Which IP address type should you use and why?

hard

A. Public IP addresses, because they allow direct internet access

B. Broadcast IP addresses, because they send data to all devices

C. Private IP addresses, because they keep devices hidden from the internet

D. Loopback IP addresses, because they test network connections

Solution

1. Step 1: Understand the purpose of private IP addresses

   Private IPs are used inside local networks to allow devices to communicate without being directly visible on the internet.

2. Step 2: Match network setup needs to IP type

   For a home network that should not expose devices directly, private IP addresses are ideal to provide local connectivity and security.

3. Final Answer:

   Private IP addresses, because they keep devices hidden from the internet -> Option C

4. Quick Check:

   Home networks use private IPs for local security [OK]

Hint: Use private IPs for local networks hidden from internet [OK]

Common Mistakes:

• Choosing public IPs and risking exposure
• Confusing broadcast or loopback IPs with usable device IPs
• Not understanding network security basics