Static NAT

Explanation

The correct answer is D. static NAT.

Static NAT is a type of NAT (Network Address Translation) where a single inside local address is statically mapped to a single outside global address. This means that every time a device with that particular inside local address initiates communication to the internet, the same outside global address is used. Static NAT is commonly used when servers or devices on the internal network need to be accessed from the outside using a fixed IP address.

Dynamic NAT, on the other hand, is a type of NAT where a pool of outside global addresses is used to dynamically map inside local addresses. This means that different inside local addresses can use different outside global addresses, depending on availability. Dynamic NAT is useful when a limited number of outside global addresses are available, as it allows multiple devices on the internal network to access the internet using the same set of outside global addresses.

NAT overload, also known as Port Address Translation (PAT), is a specific type of dynamic NAT where multiple inside local addresses are translated to a single outside global address. This is done by using different source port numbers to differentiate between the different internal devices. PAT is commonly used by home and small business routers to allow multiple devices to access the internet using a single public IP address.

In conclusion, the correct answer to the question is D. static NAT, as it is the only type of NAT that maps a single inside local address to a single outside global address.