Address Translation

NAT -Network Address Translaton (NAT)

Translates priavre ip address to public ip address for routing over public networks.

DNAT - Dynamic NAT Automatically assigs an IP address from a pool and gives a one-to-one translation like if you shared keys to car with a group of people.

SNAT - Manually assigns an ip address and gives one-to-one translation.

PAT port address translation - sharing one public IP address by multiple private ip addresses which give a many to one translation . -

Inside local - privae iP address. inside gloval private ip address refenced an outside

outside global publice ip addess refrencing an outside device.

diagram of nat working….

NAT (Network Address Translation)

Purpose

Allows devices with private IPs (RFC1918) to communicate on public networks.
Translates between private ↔ public addresses.
Conserves IPV4 addresses.

Types of NAT

Dynamic NAT (DNAT)

Uses a pool of public IPs.
Each private IP gets temporarily mapped to one public IP (one-to-one).
Analogy: “Borrowing a car key from a shared key pool.”

Static NAT (SNAT)

A fixed mapping between one private IP and one public IP.
Always the same → often used for servers that must be reachable from outside.
Analogy: “Each driver has their own permanent key.”

PAT (Port Address Translation)

(also called NAT overload)

Many private IPs share one public IP, differentiated by port numbers.
Most common type (used in home routers).
Analogy: “One car, many drivers; the system tracks who’s who by seat number.”

NAT Address Terms

Inside Local: Private IP of internal device.
Inside Global: Public IP representing that internal device to the outside.
Outside Global: Public IP of an external device.

Diagram (text version for memory)

Private LAN (Inside Local)     Router/NAT       Internet (Outside Global)
192.168.1.10  ───────────────> [NAT] ──────────&gt; 66.51.41.112
192.168.1.11  ───────────────> [NAT] ──────────&gt; 66.51.41.112:1025
192.168.1.12  ───────────────> [NAT] ──────────&gt; 66.51.41.112:1026

Here, PAT is in action: multiple inside locals mapped to a single inside global (public IP) with unique port numbers.

✅ Exam Must-Knows

Static NAT = fixed one-to-one.
Dynamic NAT = pool one-to-one.
PAT = many-to-one (common in SOHO).
Inside local = private. Inside global = translated public.
NAT is critical for IPV4 conservation.

⚡ Flashcards

Q: Which NAT type allows multiple private IPs to share one public IP?

A: PAT.
Q: Which NAT type uses a pool of public addresses?

A: Dynamic NAT.
Q: What does “inside local” mean?

A: Private IP of an internal device.
Q: What’s the most common NAT type in home routers?

A: PAT (NAT overload).