This blog post provides a deep, professional, and cybersecurity-focused explanation of a visual diagram titled:
Advanced NAT Explainer: Static, Dynamic, & PAT (Network Address Translation)
The diagram explains how Network Address Translation (NAT) works at an advanced level, showing three distinct NAT techniques:
- Static NAT (One-to-One Mapping)
- Dynamic NAT (Many-to-Many Mapping)
- PAT – Port Address Translation (Many-to-One / Overloading)
This explanation assumes no prior knowledge and explains every visible label, arrow, IP address, table, color, and traffic flow shown in the image. The explanation gradually builds toward a networking and security expert understanding.
1. What This Diagram Represents Overall
The diagram explains how private IP addresses inside a local network are translated into public IP addresses when communicating with the internet.
The layout is divided horizontally into three sections, each representing a different NAT technique.
Across all three sections, the diagram consistently shows:
- A Private Network (Inside Local) on the left
- A Router / NAT Device in the center
- A Public Network / Internet on the right
This consistent layout helps visually compare how each NAT type behaves.
2. Section 1: Static NAT (One-to-One Mapping)
The first section is labeled:
1. STATIC NAT (One-to-One Mapping)
This section demonstrates the simplest and most predictable form of NAT.
2.1 Components Shown in Static NAT
- Private Network (Inside Local)
- Web Server with Private IP: 192.168.1.10
- Router / NAT Device
- Public Network (Outside Global / Internet)
- Public Server with Public IP: 203.0.113.1
The private network and public network are visually separated using dashed boundaries, indicating different trust and addressing zones.
2.2 Static NAT Translation Table
The NAT device shows a Static NAT Table:
| Private IP | Public IP |
|---|---|
| 192.168.1.10 | 203.0.113.1 |
This mapping is permanent and fixed.
2.3 Traffic Flow in Static NAT
The arrows show:
- Outbound Traffic from private server to internet
- Reverse Translation back to the private IP
- Inbound Traffic initiated from the internet
This bidirectional arrow flow indicates that Static NAT allows connections to be initiated from either side.
2.4 Explanation Text in the Diagram
Permanent, fixed mapping. One private IP is always translated to the same public IP. Allows bidirectional initiation of traffic. Ideal for public-facing servers (web, mail).
2.5 Real-World Example
A company hosts a public web server inside its private network. Static NAT ensures the server is always reachable using the same public IP.
3. Section 2: Dynamic NAT (Many-to-Many Mapping)
The second section is labeled:
2. DYNAMIC NAT (Many-to-Many Mapping)
This section introduces temporary and session-based NAT behavior.
3.1 Components Shown in Dynamic NAT
- PC1 – 192.168.1.100
- PC2 – 192.168.1.101
- PC3 – 192.168.1.102
- Router / NAT Device
- Public IP Pool: 203.0.113.10 – 203.0.113.20
Multiple private hosts share a pool of public IP addresses.
3.2 Dynamic NAT Pool Table
| Private IP | Public IP (Leased) |
|---|---|
| 192.168.1.100 | 203.0.113.10 |
| 192.168.1.101 | 203.0.113.11 |
| 192.168.1.102 | Waiting for Available IP |
3.3 Traffic Characteristics
- Only outbound connections are initiated
- Public IPs are leased temporarily
- Mappings are session-based
- IPs return to the pool after use
The diagram labels returned traffic as:
Return Traffic (Session Based)
3.4 Explanation Text in the Diagram
Temporary mapping from a pool of public IPs. A private IP borrows the first available public IP. Once the session ends, the public IP is returned to the pool. Typically outbound-only initiation.
3.5 Real-World Example
An enterprise network with limited public IPs allows employees to browse the internet. Inbound connections are not allowed.
4. Section 3: PAT (Port Address Translation)
The third section is labeled:
3. PAT (Port Address Translation – Many-to-One / Overloading)
This is the most common NAT implementation.
4.1 Components Shown in PAT
- PC A – 192.168.1.50:1024
- PC B – 192.168.1.51:1025
- Router / PAT Device
- Single Public IP: 203.0.113.100
4.2 PAT Translation Table
| Inside Local | Inside Global |
|---|---|
| 192.168.1.50:1024 | 203.0.113.100:5001 |
| 192.168.1.51:1025 | 203.0.113.100:5002 |
4.3 Packet-Level Explanation
The diagram shows:
- Packet A sent to Web service
- Packet B sent to Mail service
Each connection is uniquely identified by a port number.
Return packets are matched using these ports, allowing multiple devices to share one public IP.
4.4 Explanation Text in the Diagram
Maps multiple private IP addresses to a single public IP address by using different source ports to distinguish connections. Most common form of NAT for home and office networks.
4.5 Real-World Example
A home router allows dozens of devices to access the internet using a single ISP-provided IP address.
5. Key Differences Summary Table
| Feature | Static NAT | Dynamic NAT | PAT |
|---|---|---|---|
| Mapping Type | One-to-One | Many-to-Many | Many-to-One |
| Inbound Allowed | Yes | No | No |
| Public IP Usage | One per host | From pool | Single IP |
6. Final Expert Summary
This diagram clearly demonstrates how NAT evolved to solve IPv4 address exhaustion while maintaining security and scalability.
- Static NAT prioritizes reachability
- Dynamic NAT balances access and conservation
- PAT maximizes efficiency and scalability
If you understand this diagram fully, you understand how modern networks survive on limited IPv4 space 🌐
