Implementing and Operating Cisco Enterprise Network Core Technologies (ENCOR) v1.2InfrastructureEasy
A network engineer is configuring a new Cisco router and needs to ensure that all internal hosts can access the internet using a single public IP address. The router should maintain a mapping of internal private IP addresses and source port numbers to the single public IP address and unique port numbers. Which NAT type should the engineer implement?
- AStatic NAT
- BTwice NAT
- CDynamic NAT
- DNAT Overload (PAT)
Show answer & explanationAnswer & explanation
Correct answer: D. NAT Overload (PAT)
NAT Overload, also known as Port Address Translation (PAT), allows multiple private IP addresses to share a single public IP address by using unique source port numbers for each conversation. This is the most common form of NAT for internet access.
Why the other options are wrong
- A. Static NAT maps one private IP address to one public IP address.
- B. Twice NAT is used for translating both source and destination IP addresses, often in specific network merging scenarios.
- C. Dynamic NAT maps multiple private IP addresses to a pool of public IP addresses, but still uses one-to-one mapping from the pool.
NAT Overload (PAT)
A type of Network Address Translation (NAT) that allows multiple internal private IP addresses to share a single public IP address by assigning unique source port numbers for each outbound connection.
- Uses port numbers for many-to-one mapping.
- Commonly used for internet access from private networks.
- Conserves public IP addresses.
Memory trick: Many homes, one gate, many keys.