NAT (Network Address Translation) in Computer Networks - Mini Project: Build & Apply

Understanding NAT (Network Address Translation)

📖 Scenario: You are learning how devices in a home network share a single public IP address to access the internet using NAT.

🎯 Goal: Build a simple representation of how NAT maps private IP addresses to a single public IP address with port numbers.

📋 What You'll Learn

Create a dictionary with private IP addresses as keys and their assigned port numbers as values.

Add a variable for the public IP address used by the NAT device.

Create a new dictionary that maps each private IP and port to a unique public port number.

Add a final mapping that shows the full NAT translation from private IP:port to public IP:port.

💡 Why This Matters

🌍 Real World

NAT is used in home and office routers to allow many devices to share one public IP address for internet access.

💼 Career

Understanding NAT is essential for network administrators and IT professionals managing network security and connectivity.

1

Create private IP addresses with ports

Create a dictionary called private_ips with these exact entries: '192.168.1.2': 1024, '192.168.1.3': 2048, and '192.168.1.4': 3072 representing private IP addresses and their port numbers.

Computer Networks

# Create the private_ips dictionary with IPs and ports
# Your code here

Need a hint?

Use curly braces to create a dictionary with the exact IP-port pairs.

2

Add the public IP address

Add a variable called public_ip and set it to the string '203.0.113.1' representing the NAT device's public IP address.

Computer Networks

private_ips = {'192.168.1.2': 1024, '192.168.1.3': 2048, '192.168.1.4': 3072}
# Add the public_ip variable below
# Your code here

Need a hint?

Assign the string '203.0.113.1' to the variable public_ip.

3

Map private IPs and ports to unique public ports

Create a dictionary called nat_table that maps each private IP and port tuple to a unique public port number starting from 40000. Use a for loop with variables ip and port to iterate over private_ips.items().

Computer Networks

private_ips = {'192.168.1.2': 1024, '192.168.1.3': 2048, '192.168.1.4': 3072}
public_ip = '203.0.113.1'
# Create nat_table dictionary mapping (ip, port) to public ports starting at 40000
# Your code here

Need a hint?

Use a for loop to assign increasing public ports starting at 40000 to each private IP and port pair.

4

Create full NAT translation mapping

Create a dictionary called full_nat_mapping that maps each private IP and port tuple to a string combining public_ip and the corresponding public port from nat_table in the format 'public_ip:public_port'. Use a for loop with variables key and pub_port to iterate over nat_table.items().

Computer Networks

private_ips = {'192.168.1.2': 1024, '192.168.1.3': 2048, '192.168.1.4': 3072}
public_ip = '203.0.113.1'
nat_table = {}
public_port = 40000
for ip, port in private_ips.items():
    nat_table[(ip, port)] = public_port
    public_port += 1
# Create full_nat_mapping dictionary mapping private IP:port to 'public_ip:public_port' strings
# Your code here

Need a hint?

Use a for loop to build strings combining public_ip and public port for each private IP and port.