Name and describe the common IPv4 NAT types: static, dynamic, and PAT.

• A. Static NAT maps a fixed private address to a public address; Dynamic NAT uses a pool of public addresses; PAT maps many private addresses to a single public address using ports.
• B. Dynamic NAT maps a private address to a public address on a pool; Static NAT uses a fixed private address.
• C. PAT maps a fixed private address to a public address; Static NAT uses a pool of public addresses.
• D. NAT translates addresses in both directions without port translation.

Answer: (C)

NAT types differ in how they map internal addresses to the public Internet and whether ports are used to distinguish connections.

Static NAT is a one-to-one, permanent mapping from a specific private IP to a specific public IP. The internal host always appears with the same public address, so external systems see a fixed address for that device.

Dynamic NAT uses a pool of public addresses. When an internal host connects, NAT assigns one available public address from the pool for the duration of the session. The mapping isn’t fixed to a single external address and can change if the host reconnects or if the pool assignment changes; this requires available addresses in the pool.

PAT, also called NAT overload, maps many private addresses to a single public IP by using unique port numbers for each connection. This allows many internal hosts to share one public address, with ports keeping each flow separate so responses are delivered to the correct internal host.

So the three concepts are: static NAT for fixed one-to-one mappings, dynamic NAT for pool-based mappings, and PAT for port-based sharing of a single public address.