A PAT in networking stands for Port Address Translation, a type of Network Address Translation (NAT).
Understanding PAT
PAT allows multiple devices on a private network to share a single public IP address. This is crucial for conserving IPv4 addresses, as the number of available public IPv4 addresses is limited.
How PAT Works
- Private to Public Mapping: PAT maps private IPv4 addresses within a network to a single public IP address. This is accomplished by using different port numbers.
- NAT Foundation: PAT is a type of NAT (Network Address Translation), a process used by routers to translate internal, non-registered IP addresses to external, registered IP addresses.
Example Scenario
Imagine a home network with several devices (computers, smartphones, etc.), all using private IP addresses (e.g., 192.168.1.x). When these devices access the internet, the router uses PAT.
- Each device sends traffic to the router.
- The router replaces the device's private IP address with its own public IP address.
- The router assigns a unique port number to each connection.
- When the external server responds, the router uses the port number to determine which internal device should receive the data.
Benefits of PAT
- IPv4 Address Conservation: One of the primary benefits. PAT enables multiple devices to share a single public IP address, reducing the need for a unique public IP address for each device.
- Enhanced Security: PAT hides the internal IP addresses of devices on a private network, adding a layer of security against direct attacks from the internet.
PAT vs. NAT
While PAT is a form of NAT, it's more specific. NAT can also refer to a one-to-one mapping where each private IP address is translated to a unique public IP address. PAT, on the other hand, is always a many-to-one (or many-to-few) mapping, utilizing port numbers to distinguish between connections.
