Describe IPv4 NAT concepts and differentiate between static NAT, dynamic NAT, and PAT (NAT with port translation).

• A. NAT translates private IPs to public IPs; static NAT uses a pool of public addresses.
• B. NAT uses port translation to multiplex multiple private addresses on a single public address.
• C. NAT maps private to public addresses; static NAT is one-to-one; dynamic NAT uses a pool; PAT uses port numbers to multiplex.
• D. NAT hides all internal addresses from the internet.

Answer: (C)

NAT’s job is to let devices on a private IPv4 network reach the public Internet by translating private addresses to public ones. In static NAT, there is a one-to-one relationship between a private address and a specific public address, so the mapping is permanent and the external world can reach that host using the fixed public address. Dynamic NAT uses a pool of public addresses; when a private host needs Internet access, NAT assigns an available address from the pool for the duration of the session, returning it to the pool when done. PAT, or NAT with port translation, allows many private hosts to share a single public address by translating the private source ports to distinct public ports; a translation table tracks each internal IP:port to a unique public IP:port so responses are delivered correctly. This combination—mapping private to public addresses; static NAT as one-to-one; dynamic NAT using a pool; and PAT using ports to multiplex—captures the different NAT concepts.