?– Inside global address: A legitimate IPv4 address assigned by the NIC or service
provider that represents one or more inside local IPv4 addresses to the outside world.
?– Outside local address: The IPv4 address of an outside host as it appears to the inside
network. Not necessarily legitimate, the outside local address is allocated from a
routable address space on the inside.
?– Outside global address: The IPv4 address that is assigned to a host on the outside
network by the host owner. The outside global address is allocated from a globally
routable address or network space.
NAT has many forms and can work in the following ways:
?– Static NAT: Maps an unregistered IPv4 address to a registered IPv4 address (one to
one). Static NAT is particularly useful when a device must be accessible from outside
the network.
?– Dynamic NAT: Maps an unregistered IPv4 address to a registered IPv4 address from
a group of registered IPv4 addresses.
?– NAT overloading: Maps multiple unregistered IPv4 addresses to a single registered
IPv4 address (many to one) by using different ports. Overloading is also known as PAT
and is a form of dynamic NAT.
NAT offers these bene?¬?ts over using public addressing:
?– Eliminates the need to readdress all hosts that require external access, saving time and
money.
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