Network Address Translation (NAT)

Lesson Objectives

By the end of this lesson, you will:

Understand the concept and purpose of Network Address Translation (NAT).
Learn the different types of NAT and their use cases.
Explore the benefits and limitations of NAT.
Practice NAT configuration through examples and exercises.

NAT Configuration Example

Scenario:

You have a private network (192.168.1.0/24) that needs Internet access through a public IP (203.0.113.1).

Static NAT (Mapping one private IP to one public IP):

 ip nat inside source static 192.168.1.10 203.0.113.1

Dynamic NAT (Mapping multiple private IPs to a pool of public IPs):

 ip nat pool PUBLIC_POOL 203.0.113.10 203.0.113.20 netmask 255.255.255.0 access-list 1 permit 192.168.1.0 0.0.0.255 ip nat inside source list 1 pool PUBLIC_POOL

PAT (Overloading a single public IP):

 ip nat inside source list 1 interface GigabitEthernet0/0 overload

Hands-On Exercises

Exercise 1: Configure PAT on a Router

Scenario: You have a private network (192.168.2.0/24) and one public IP (203.0.113.2) for Internet access.

Set up an access list:

 access-list 1 permit 192.168.2.0 0.0.0.255

Configure PAT:

 ip nat inside source list 1 interface GigabitEthernet0/0 overload

Test connectivity by pinging an external server from a private IP.

Exercise 2: Troubleshoot NAT Configuration

Problem: Devices in the private network cannot access the Internet.

Check the NAT configuration:
```
 show ip nat translations 
```
Verify NAT rules:
```
 show running-config 
```
Ensure proper ACL and interface settings.

Reflection: Why NAT is Crucial

Address Conservation: Vital for managing limited IPv4 space.
Flexibility: Enables seamless private-to-public communication.
Security: Adds a layer of protection by masking internal network details.

What’s Next?

In the next chapter, we’ll explore Virtual Private Networks (VPNs) and how they secure communication across public networks.

Your NAT skills are developing—let’s keep building! 🚀

Introduction to Computer Networks