What Is NAT? (Network Address Translation Explained Simply)
NAT (Network Address Translation) is one of the most important concepts in modern networking.
It allows multiple devices on a private network to share one public IP address when accessing the internet.
Why NAT Exists
There are not enough public IPv4 addresses for every device in the world.
NAT solves this by allowing private IP addresses (like 192.168.x.x) to be translated into a single public IP address.
Think of NAT as a receptionist at an office building — it sends outgoing requests and remembers who asked.
How NAT Works
Example:
- Your computer: 192.168.1.25
- Router (Default Gateway): 192.168.1.1
- Public IP: 73.45.88.200
When you visit a website:
1. Your computer sends traffic to the router.
2. The router replaces your private IP with its public IP.
3. The website responds to the public IP.
4. The router sends the response back to your computer.
Types of NAT
- Static NAT – One private IP maps to one public IP
- Dynamic NAT – Pool of public IPs
- PAT (Port Address Translation) – Most common; multiple devices share one public IP
PAT is what most home routers use.
How NAT Appears on the A+ Exam
Questions may ask:
- Why can multiple devices use one public IP?
- What allows private IP addresses to access the internet?
- What device performs NAT?
Correct answer:
The router performs NAT.
Troubleshooting Example
If devices have:
- Valid IP address
- Valid subnet mask
- Valid default gateway
But still no internet…
The router’s NAT function may be misconfigured.
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