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Difficulty: MediumNAT and PAT Implementation

A network administrator is configuring network address translation on an edge router for a company network. An internal public-facing web server at 192.168.1.50192.168.1.50 must be reachable from the internet at all times using a dedicated public address 203.0.113.10203.0.113.10. At the same time, 250 internal user workstations on the 192.168.1.0/24192.168.1.0/24 subnet require outbound internet connectivity using the single WAN interface IP address 203.0.113.1203.0.113.1. Which combination of NAT translation types should the administrator implement to satisfy both requirements?

  1. Configure a Static NAT mapping for the internal web server to 203.0.113.10203.0.113.10, and configure Port Address Translation (PAT/Overload) using the WAN interface for the workstation subnet.Answer
  2. B
    Configure a Dynamic NAT pool containing 203.0.113.10203.0.113.10 for the workstations, and configure Port Address Translation (PAT) for the web server.
  3. C
    Configure Static NAT for all 250 workstations using port 80 mapping, and configure Dynamic NAT for the web server using port 443.
  4. D
    Configure Layer 2 MAC address translation to map internal workstation MAC addresses directly to the WAN interface IP address.

Answer

Configure a Static NAT mapping for the internal web server to 203.0.113.10203.0.113.10, and configure Port Address Translation (PAT/Overload) using the WAN interface for the workstation subnet.
Static NAT provides a permanent one-to-one mapping between an internal private IP and an external public IP, which is required for inbound traffic destined for internal web servers. Port Address Translation (PAT), also known as NAT Overload, allows multiple internal hosts to share a single public IP address simultaneously by multiplexing connection streams using unique Layer 4 port numbers.

Step-by-Step Solution

1
Analyze the web server requirement
Inbound access requires a consistent, permanent 1-to-1 mapping between a private IP (192.168.1.50192.168.1.50) and a public IP (203.0.113.10203.0.113.10). This requires Static NAT.
External users initiating connections to an internal server require a fixed public IP address.
2
Analyze the workstation subnet requirement
250 internal hosts need outbound access sharing a single public IP address (203.0.113.1203.0.113.1). This requires Port Address Translation (PAT / NAT Overload).
PAT tracks individual sessions by mapping unique source transport port numbers to the single public IP address.
3
Combine the translation strategies
Implement Static NAT for the web server and PAT (Overload) for the internal subnet.
This hybrid approach fulfills both persistent inbound reachability and high-density outbound client access.

Key Concept

Static NAT vs. PAT (NAT Overload) Implementation
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Topics

NAT and PAT Implementation

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