Cisco CCNA (200-301)Network FundamentalsHard
A network administrator configures a router so that multiple internal hosts share a single public IPv4 address for internet access, with each session distinguished by a unique source port number. Which technique is being used?
- ADynamic NAT
- BNAT64
- CPort Address Translation (PAT)
- DStatic NAT
Show answer & explanationAnswer & explanation
Correct answer: C. Port Address Translation (PAT)
PAT, also known as NAT overload, allows many internal private addresses to share a single public IP address by tracking sessions using unique source port numbers. Static NAT maps one private address to one public address permanently, dynamic NAT maps from a pool without port sharing, and NAT64 translates between IPv6 and IPv4.
Why the other options are wrong
- A. Dynamic NAT maps addresses from a pool one-to-one, without necessarily sharing a single address via ports.
- B. NAT64 translates between IPv6 and IPv4 address families, unrelated to this scenario.
- D. Static NAT is a fixed one-to-one mapping, not a many-to-one shared address scheme.
Port Address Translation (PAT)
PAT, or NAT overload, allows multiple private hosts to share a single public IP address by using unique source port numbers to differentiate simultaneous sessions.
- Also called NAT overload
- Most common form of NAT on home/SOHO routers
- Uses source port numbers to multiplex sessions
- Conserves public IPv4 addresses
Memory trick: PAT = 'Ports Allow The share' of one IP by many.