Network Address Translation (NAT) is a technique that allows multiple devices on a private network to share one or more public IP addresses when communicating with the Internet.
Today, NAT is used in almost every home and office network.
Most devices use private IP addresses, which cannot be routed across the Internet.
For example:
Laptop 192.168.1.20
A website on the Internet cannot send packets directly to this address.
Instead, a router performs Network Address Translation (NAT).
Suppose your home router has:
Public IP 203.0.113.25
Your laptop has:
Private IP 192.168.1.20
When you visit:
https://example.com
the router replaces the source address.
Before NAT:
Source 192.168.1.20 Destination 93.184.216.34
After NAT:
Source 203.0.113.25 Destination 93.184.216.34
The website never sees your private IP address.
Laptop
192.168.1.20
│
Phone
192.168.1.21
│
TV
192.168.1.22
│
▼
Wi-Fi Router
NAT
Public IP
203.0.113.25
│
▼
Internet
All three devices share the same public IPv4 address.
IPv4 provides about:
4.3 billion addresses
This is not enough for every Internet-connected device.
NAT allows thousands of devices to share a much smaller number of public addresses.
Without NAT, IPv4 exhaustion would have occurred much earlier.
NAT also has some drawbacks.
IPv6 provides an enormous address space.
Therefore, IPv6 generally does not require NAT.
Each device can have its own globally unique IPv6 address.
Some Internet Service Providers perform NAT on their own networks.
This is called Carrier-Grade NAT (CGNAT).
Example:
Your Computer ↓ Home Router ↓ ISP NAT ↓ Internet
With CGNAT:
Several Telenegar tools help illustrate NAT.
IP Check
Your computer may have:
192.168.1.20
while Telenegar reports:
203.0.113.25
This difference is usually caused by NAT.
Traceroute
When using Telenegar Traceroute, the first hop is often your home router.
Example:
1 192.168.1.1 2 ISP Gateway 3 ...
The first hop is the device performing NAT and forwarding your traffic toward the Internet.
nat ipv4 ipv6 networking traceroute ipcheck