Cisco Certified Support Technician (CCST) NetworkingIP ConnectivityMedium
A small branch office uses a single public IP address provided by its ISP. Due to growth, the office now needs to host an internal web server (192.168.1.100) that must be accessible from the internet using a specific public IP address (203.0.113.50), which is part of a small block assigned to the office. All other internal hosts should continue to use the existing PAT configuration. Which NAT configuration type is required for the web server?
- AStatic NAT
- BPAT (Port Address Translation)
- CDynamic NAT
- DNAT Overload
Show answer & explanationAnswer & explanation
Correct answer: A. Static NAT
Static NAT is used to create a one-to-one mapping between a private IP address and a public IP address. This is essential for servers or devices that need to be consistently accessible from the internet using a fixed public IP address, such as a web server. Dynamic NAT and PAT are for outbound connections where multiple private IPs share public IPs, but they don't guarantee a consistent, inbound-routable public IP for a specific internal host.
Why the other options are wrong
- B. PAT (also known as NAT Overload) allows many private IPs to share one public IP using port numbers, primarily for outbound connections, not for consistent inbound access to a specific server.
- C. Dynamic NAT maps private IPs to a pool of public IPs, but the mapping is not fixed or consistent for inbound access.
- D. NAT Overload is another name for PAT, which has the same limitations as option C for this scenario.
Static NAT
Static Network Address Translation (NAT) creates a one-to-one, permanent mapping between a specific private IP address and a specific public IP address.
- Used for servers or devices needing consistent inbound access from the internet.
- Mapping is always maintained in the NAT table.
- Consumes one public IP address per translated private IP.
Memory trick: NAT types are like different doors: some for many, some for one-to-one.