CCNA Network Services and Security Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Use transport-layer port values to distinguish multiple inside sessions behind one outside address.

  Why this is correct

  Port Address Translation (PAT) multiplexes thousands of internal hosts through a single public IPv4 address by rewriting the source port along with the source IP in each packet. The NAT router builds a session table that maps each inside local address and TCP/UDP port to the outside global address plus a unique translated port, allowing return traffic to be correctly demultiplexed. This is exactly how one outside address can simultaneously support many inside sessions.

• ✗

  Convert all inside hosts to the same private IP address.

  Why it's wrong here

  Assigning every inside host the same private IP address would create Layer 3 addressing conflicts, breaking ARP and preventing any host from communicating on the LAN. PAT assumes each inside host retains its own unique private IPv4 address so the router can track individual sessions; the translation process then maps those unique local addresses to a shared public address with different port numbers. Thus, a common private IP is neither required nor usable.

  When this WOULD be correct

  In a scenario where a question asks how to simplify IP address management in a small network with only one device needing external access, and all devices are in a trusted environment, this option could be correct if it implies using a single private IP for a specific application or service.

• ✗

  Increase the size of the NAT pool to include multiple public addresses.

  Why it's wrong here

  Expanding the NAT pool to include more public addresses is characteristic of dynamic NAT or many-to-many translation, not of PAT. In PAT, even with a pool of addresses, the distinguishing mechanism is still the transport-layer port number, and the router will overload the available addresses by reusing them with different source ports. Simply adding more public IPs does not enable port-based session multiplexing, which is the core feature that PAT uses to handle many inside sessions.

  When this WOULD be correct

  In a different scenario where the question asks about isolating internal traffic for security purposes, disabling the default route could be correct if the goal is to ensure that internal hosts do not communicate with the outside world, thereby enhancing security.

• ✗

  Configure static NAT mappings for each inside host.

  Why it's wrong here

  Configuring static NAT for each host requires a one-to-one mapping between an inside local address and an inside global address, meaning you need one public IPv4 address per host. That defeats the purpose of PAT, which is designed to conserve public address space by allowing many hosts to share a single outside address through port multiplexing. Static NAT also does not scale for even a small office and fails to provide the transport-layer port translation that PAT implements.

  When this WOULD be correct

  In a scenario where the question asks about optimizing VLAN configurations for multiple subnets to communicate over a single physical link, changing access ports to trunk ports would be correct to allow multiple VLANs to share the same infrastructure while maintaining separation.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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