CompTIA Network+ (N10-009)Networking ConceptsMedium
A small business has only one public IP address but needs to allow dozens of internal devices to access the internet simultaneously. Which technology allows all devices to share the single public IP by distinguishing sessions with different port numbers?
- APAT (Port Address Translation)
- BStatic NAT
- CDynamic NAT
- DAnycast
Show answer & explanationAnswer & explanation
Correct answer: A. PAT (Port Address Translation)
PAT (also called NAT overload) allows many internal private IP addresses to share a single public IP by mapping each session to a unique port number, making it ideal for small networks with limited public addresses.
Why the other options are wrong
- B. Static NAT maps one private IP to one public IP permanently, not shared among many devices.
- C. Dynamic NAT maps private IPs to a pool of public IPs on a one-to-one basis, still limited by pool size.
- D. Anycast routes traffic to the nearest of multiple identical IP addresses, unrelated to address sharing.
PAT (Port Address Translation)
PAT, or NAT overload, allows multiple internal devices to share one public IP address by assigning unique port numbers to each session.
- Also called NAT overload
- Maps many private IPs to one public IP
- Uses port numbers to track individual sessions
Memory trick: PAT packs many devices behind one public port-labeled door.