Port Address Translation (PAT), also known as NAT Overload, is a function of Network Address Translation (NAT) that allows multiple devices on a private local area network (LAN) to be mapped to a single public IP address for accessing the internet. It conserves IP addresses by using different TCP/UDP port numbers to distinguish between traffic from different internal clients. When a client sends a request to the internet, the PAT-enabled router translates the private source IP and source port to its own public IP and a unique ephemeral port, tracking this mapping in a translation table. This allows many internal users to share one public IP address simultaneously.

A. STP (Spanning Tree Protocol) is a Layer 2 protocol that prevents broadcast storms and logical loops in a network with redundant switch paths; it does not manage IP addresses.

B. BGP (Border Gateway Protocol) is an exterior gateway protocol used to exchange routing and reachability information among autonomous systems (AS) on the internet, not for local IP address sharing.

D. VXLAN (Virtual Extensible LAN) is a network virtualization technology used to create logical Layer 2 networks over a Layer 3 infrastructure, primarily in data centers and cloud environments.

1. Internet Engineering Task Force (IETF) RFC 3022: Srisuresh

P.

& Egevang

K. (2001). Traditional IP Network Address Translator (Traditional NAT). RFC 3022. Section 2.1

"NAPT

" describes Network Address Port Translation (the official term for PAT)

stating

"NAPT allows a set of hosts in a private network to share a single registered IP address."

2. Cisco Systems

Inc. Official Documentation: "IP Addressing: NAT Configuration Guide

Cisco IOS XE Gibraltar 16.12.x". In the "NAT Overload" section

it states

"You can conserve addresses in the inside global address pool by allowing the router to use one global address for many local addresses. When this overloading is configured

the router maintains enough information from higher-level protocols (for example

TCP or UDP port numbers) to translate the global address back to the correct local address."

3. University of California

Berkeley Courseware: "CS 168: Introduction to the Internet: Architecture and Protocols

" Lecture 10: NAT & Tunnels. The lecture notes explain that NAT Overload (PAT) maps multiple private hosts to a single public IP address by rewriting the source port

which is the exact scenario described in the question.