Free CCNA | NAT (part 2) | Day 45 | CCNA 200-301 Complete Course

Introduction

This tutorial covers the concepts of Network Address Translation (NAT), specifically focusing on Dynamic NAT and Port Address Translation (PAT), as explained in the video titled "Free CCNA | NAT (part 2) | Day 45 | CCNA 200-301 Complete Course" by Jeremy's IT Lab. Understanding NAT is crucial for network engineers, as it plays an essential role in IP address management and network security.

Step 1: Review Static NAT

• Definition: Static NAT maps a single private IP address to a single public IP address. This is often used for servers that need to be consistently reachable from the outside.
• Key Points:
  • Each internal host must have a unique static mapping.
  • Static NAT does not conserve IP addresses as it assigns a public IP for every private IP.
• Practical Tip: Use Static NAT for devices that require a constant public IP, such as web servers.

Step 2: Understand Dynamic NAT

• Definition: Dynamic NAT allows multiple private IP addresses to be mapped to a pool of public IP addresses. It assigns a public IP from the pool on a first-come, first-served basis.
• Key Points:
  • If the pool of public IPs is exhausted, additional hosts will not be able to access the internet.
  • Dynamic NAT is more efficient than Static NAT as it conserves public IP addresses.
• Common Pitfall: Ensure the NAT pool has enough IP addresses to handle peak usage, otherwise, connectivity issues will arise.

Step 3: Configure Dynamic NAT

1. Define a NAT pool:

   • Use the following command in global configuration mode:

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

   • Example:

     ip nat pool MY_POOL 192.168.1.1 192.168.1.5 netmask 255.255.255.0
     

2. Define the access list:

   • Create an access list to identify which internal IPs can use the NAT pool:

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

   • Example:

     access-list 1 permit 192.168.1.0 0.0.0.255
     

3. Associate the access list with the NAT pool:

   • Use the command:

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

Step 4: Learn About PAT (NAT Overload)

• Definition: PAT allows multiple devices on a local network to be mapped to a single public IP address, distinguished by different ports. This is widely used for home networks.
• Key Points:
  • PAT conserves IP addresses, making it ideal for environments with many devices but limited public IPs.
  • Each internal device uses a unique port number to communicate with the outside world.

Step 5: Configure PAT

1. Use the same NAT pool:

   • You can use the same public IP from the previous NAT pool configuration.

2. Define PAT using the interface:

   • Enter the following command in global configuration mode:

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

   • Example:

     ip nat inside source list 1 interface Serial0/0 overload
     

Step 6: Review NAT Commands

• Familiarize yourself with essential NAT commands:
  • show ip nat translations: Displays current NAT translations.
  • show ip nat statistics: Provides NAT statistics, including pool usage.

Conclusion

In this tutorial, you learned the fundamentals of NAT, including Static NAT, Dynamic NAT, and PAT. You also explored configuration steps for both Dynamic NAT and PAT, along with common pitfalls to avoid. Familiarizing yourself with these concepts and commands will enhance your capabilities as a network engineer. For further practice, consider using simulation tools or labs available in the course resources.