Dual Stack is a networking approach that involves running both IPv4 and IPv6 protocols on the same network infrastructure. This allows devices to communicate using either protocol, depending on their capabilities and the availability of network resources.
As the adoption of IPv6 is still not yet widespread, many Internet Service Providers (ISPs) continue to rely heavily on IPv4. As a result, they have implemented Carrier Grade Network Address Translation (CGNAT) to extend the lifetime of their IPv4 address pools and to cope with the increasing number of devices that require an Internet connection.
CGNAT works by allowing multiple customers to share a single public IPv4 address. This is achieved by assigning private IPv4 addresses to devices within the customer's network, and then mapping these addresses to the shared public IPv4 address when traffic is sent to and from the Internet.