How to Configure NAT Overload or Port Address Translation (PAT)

In this video, the presenter demonstrates how to configure Network Address Translation (NAT) overload, also known as Port Address Translation (PAT), using two 2911 series routers and a switch. The setup involves connecting the devices with serial cables and configuring their interfaces with a small /30 subnet for internal communication. First, the presenter configures the serial port on the routers and assigns IP addresses, ensuring connectivity between the devices through ping tests. The routing table is set up to point to the ISP router, eliminating the need for additional routes since the internal networks are reachable. Next, the inside and outside interfaces for NAT are defined, along with an access list to permit specific IP addresses. The rationale for using PAT is explained, emphasizing the efficiency of using a single public IP address for multiple devices to prevent IP address depletion. The video shows the IP NAT translation table, which starts empty, and then initiates communication to a web server. As devices communicate, they receive the assigned public IP address, demonstrating the NAT overload functionality. The video concludes with a practical demonstration of the setup.