Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureEasy
A network engineer is configuring a Cisco router to provide Internet access for a small office. The office has a single public IP address, but multiple internal devices need to access the Internet simultaneously. Which NAT type allows multiple internal private IP addresses to share a single public IP address by using different port numbers?
- AStatic NAT
- BDynamic NAT
- CNAT Overload (PAT)
- DNAT64
Show answer & explanationAnswer & explanation
Correct answer: C. NAT Overload (PAT)
NAT Overload, also known as Port Address Translation (PAT), allows multiple internal private IP addresses to share a single public IP address by mapping different source port numbers to distinguish between the internal hosts. This is the most common form of NAT used for Internet access in small offices.
Why the other options are wrong
- A. Static NAT maps a single private IP address to a single public IP address, one-to-one.
- B. Dynamic NAT maps a pool of private IP addresses to a pool of public IP addresses, but still one-to-one at any given time.
- D. NAT64 is used for translating IPv6 packets to IPv4 packets and vice-versa, not for sharing a single public IPv4 address among multiple private ones.
NAT Overload (PAT)
A form of Network Address Translation (NAT) that allows multiple internal private IP addresses to share a single public IP address by using unique source port numbers for each connection.
- Also known as Port Address Translation (PAT).
- Most common NAT type for Internet access in SOHO/SMB.
- Conserves public IP addresses.
Memory trick: PAT Portions Public Address Power