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Difficulty: MediumNAT and PAT Implementation

A network administrator is managing a border router connected to a single public IP address. The router is currently configured with Port Address Translation (PAT) to allow 200 internal workstations on the private network to access the internet simultaneously. The organization installs a new internal web server at IP address 10.0.5.2510.0.5.25 that must be publicly accessible from the internet on standard HTTP TCP port 80. Remote external users report that connections to the web server time out, while internal workstations continue to access external websites without issue. Which network address translation configuration should the administrator implement on the router to enable inbound access to the web server without disrupting existing outbound client traffic?

  1. Static NAT (Port Forwarding) mapping incoming traffic on public TCP port 80 to internal IP address 10.0.5.25Answer
  2. B
    Dynamic NAT configured with a translation pool consisting of the router's single public IP address
  3. C
    Reconfiguring PAT to route incoming Layer 2 frame headers directly to the internal server's MAC address
  4. D
    Changing the web server transport protocol to UDP port 80 to permit bi-directional PAT session traversal

Answer

Static NAT (Port Forwarding) mapping incoming traffic on public TCP port 80 to internal IP address 10.0.5.25
Static NAT (or Port Forwarding) establishes a persistent translation rule mapping incoming traffic on a specific public IP and port (TCP 80) to the private IP address of the internal web server (10.0.5.2510.0.5.25). This enables external clients to reach the web server while preserving the existing PAT configuration for outbound internal traffic.

Step-by-Step Solution

1
Analyze the technical requirements and existing configuration
Outbound hosts share one public IP address via PAT (many-to-one translation). The internal web server requires a static inbound translation rule on a specific port.
PAT dynamically maps ephemeral source ports for outbound connections but does not open persistent inbound listening ports for external requests.
2
Evaluate NAT types for inbound service publishing
Static NAT (specifically static PAT or port forwarding) explicitly routes external packets arriving on public TCP port 80 to private IP address 10.0.5.2510.0.5.25.
Port forwarding allows a single public IP address to simultaneously host internal server services and process outbound PAT traffic.

Key Concept

Static NAT and Port Forwarding for Inbound Service Accessibility
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Topics

NAT and PAT Implementation

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