Which type of IP pool allows many internal IPs to share a single external IP?

The correct choice is characterized by its ability to enable multiple internal devices to connect to the internet using a single external IP address. This method is known as PAT (Port Address Translation) or overload NAT, which allows a router or firewall to manage multiple internal IP addresses by mapping them to a single external IP address with the use of different port numbers.

As multiple internal devices initiate connections, each is assigned a unique port number for tracking. This significantly conserves the number of externally allocated IP addresses, making it useful in scenarios where IP address scarcity is a concern. The efficient use of resources in this method is vital for many organizations, especially those with numerous internal devices that require internet access.

In contrast, the other types of IP pools do not offer this allocation flexibility. For instance, a one-to-one IP pool assigns a unique external IP address for each internal IP address, which does not facilitate sharing or save external IP addresses. Fixed port range and port block allocation offer specific configurations for managing port mapping but do not effectively share a single external IP among multiple internal IPs like the overload option does.