Configuring dynamic NAT with a pool

Introduction

This tutorial will guide you through the process of configuring dynamic NAT (Network Address Translation) using a NAT pool on a Cisco router. Dynamic NAT allows multiple private IP addresses to be mapped to a pool of public IP addresses, enabling devices on a private network to access the internet. This setup is crucial for conserving public IP addresses and ensuring proper routing. You can also follow along using the provided Packet Tracer file.

Step 1: Set Up the Cisco Router

• Access your Cisco router through the console or terminal.
• Enter privileged EXEC mode by typing:

  enable
  

• Access global configuration mode by typing:

  configure terminal
  

Step 2: Define the NAT Pool

• Create a NAT pool by defining the range of public IP addresses you want to use. Use the following command structure:

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

• Example:

  ip nat pool my-nat-pool 203.0.113.1 203.0.113.10 netmask 255.255.255.0
  

Step 3: Configure Access List

• Create an access list to define which internal IP addresses are allowed to use the NAT pool. Use the following command:

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

• Example:

  access-list 1 permit 192.168.1.0 0.0.0.255
  

Step 4: Bind the NAT Pool to the Access List

• Link the NAT pool to the access list using the following command:

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

• Example:

  ip nat inside source list 1 pool my-nat-pool
  

Step 5: Configure Interfaces

• Designate the inside and outside interfaces of the router. Use the following commands:
  • For the inside interface:

    interface [interface-name]
    ip nat inside
    

  • For the outside interface:

    interface [interface-name]
    ip nat outside
    

• Example:

  interface GigabitEthernet0/0
  ip nat inside
  interface GigabitEthernet0/1
  ip nat outside
  

Step 6: Verify NAT Configuration

• To check the NAT configuration and ensure it is working properly, use the following command:

  show ip nat translations
  

• You can also check for any issues in the NAT configuration by running:

  show ip nat statistics
  

Conclusion

You have successfully configured dynamic NAT with a NAT pool on your Cisco router. This setup allows multiple devices on your internal network to access the internet using a limited number of public IP addresses. For further practice, explore additional configurations such as static NAT or PAT (Port Address Translation). Download the Packet Tracer file to experiment further and reinforce your understanding.