Free CCNA | Dynamic NAT | Day 45 Lab | CCNA 200-301 Complete Course

Introduction

In this tutorial, we will explore the configuration of Dynamic Network Address Translation (NAT) and Port Address Translation (PAT) as part of the CCNA 200-301 lab exercises. This guide is designed to help you understand the practical steps involved in setting up NAT and PAT, which are essential for managing IP address conservation and enhancing network security.

Step 1: Understanding NAT and PAT

• Network Address Translation (NAT) allows multiple devices on a local network to access the internet using a single public IP address.
• Port Address Translation (PAT), also known as NAT overload, enables multiple devices to be mapped to a single public IP address but with different port numbers.

Practical Advice:

• Familiarize yourself with the concepts of inside local, inside global, outside local, and outside global addresses.
• Understand that NAT helps in conserving public IP addresses and adds a layer of security by obscuring internal IP addresses.

Step 2: Setting Up Dynamic NAT

1. Access the Router using the command-line interface (CLI).
2. Define the NAT Pool:
   • Use the command:

     ip nat pool [name] [start-ip] [end-ip] netmask [subnet-mask]
     

   • Example:

     ip nat pool MY_POOL 192.168.1.100 192.168.1.200 netmask 255.255.255.0
     

3. Create an Access List:
   • Define which internal IP addresses will use NAT:

     access-list [number] permit [source-ip] [wildcard-mask]
     

   • Example:

     access-list 1 permit 192.168.1.0 0.0.0.255
     

4. Configure NAT:
   • Use the command to bind the access list to the NAT pool:

     ip nat inside source list [access-list-number] pool [pool-name]
     

Practical Advice:

• Verify your configuration using the command show ip nat translations to ensure NAT is functioning correctly.
• Check the command show ip nat statistics for a summary of NAT operations.

Step 3: Configuring PAT

1. Identify the Inside Interface:
   • Use the command:

     interface [inside-interface]
     ip nat inside
     

2. Identify the Outside Interface:
   • Use the command:

     interface [outside-interface]
     ip nat outside
     

3. Configure PAT:
   • Use the command to enable PAT:

     ip nat inside source list [access-list-number] interface [outside-interface] overload
     

   • Example:

     ip nat inside source list 1 interface Serial0/0/0 overload
     

Practical Advice:

• Ensure that the access list used for PAT includes all internal devices that need internet access.
• Use show ip nat translations to verify that translations are created for internal devices.

Step 4: Testing NAT and PAT Configuration

1. Ping an External IP Address:
   • Use a device within the internal network to ping a known external IP.
2. Check NAT Translations:
   • Use the command:

     show ip nat translations
     

   • Ensure that the internal IP addresses are being translated to the public IP address.
3. Verify Connectivity:
   • Browse the internet from an internal device to confirm that NAT/PAT is working.

Practical Advice:

• Use packet capturing tools to analyze the traffic and validate that NAT is functioning correctly.
• If issues arise, check for misconfigurations in the NAT settings and access lists.

Conclusion

This tutorial provided a step-by-step guide to configuring Dynamic NAT and PAT on a Cisco router. By following these steps, you will be able to manage IP address usage effectively and secure your internal network. For further practice, consider using tools like Boson NetSim to simulate NAT configurations in a controlled environment.