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300-410 Practice Question: Runs the following command on Router R1: R1# show…

A network engineer runs the following command on Router R1:

R1# show ip nat translations

Pro Inside global Inside local Outside local Outside global tcp 192.0.2.10:80 10.0.0.10:80 203.0.113.5:12345 203.0.113.5:12345 tcp 192.0.2.10:80 10.0.0.11:80 203.0.113.5:67890 203.0.113.5:67890

R1# show ip nat statistics

Total active translations: 2 (0 static, 2 dynamic; 2 extended) Outside interfaces: GigabitEthernet0/1 Inside interfaces: GigabitEthernet0/0 Hits: 50 Misses: 0 CEF Translated packets: 50, CEF Punted packets: 0 Expired translations: 0 Dynamic mappings: -- Inside Source

[Id] ip nat inside source list ACL1 interface GigabitEthernet0/1 overload

refcount 2

Based on this output, what is the problem?

⚠ Common exam trap

Cisco often tests the misconception that PAT always works automatically without verifying unique port assignments, leading candidates to overlook the duplicate port issue in the translation output.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

PAT is not assigning unique source ports; both translations use port 80, which will cause conflicts.

The output shows two dynamic NAT translations mapping different inside local hosts (10.0.0.10 and 10.0.0.11) to the same inside global IP address (192.0.2.10) and the same source port (80). PAT (Port Address Translation) should assign unique source ports to differentiate the sessions, but here both translations use port 80, which will cause conflicts when return traffic arrives because the router cannot determine which inside host should receive the packet. This indicates a misconfiguration or a bug where PAT is not performing port overload correctly.

Answer analysis

Option-by-option breakdown

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

  • PAT is not assigning unique source ports; both translations use port 80, which will cause conflicts.

    Why this is correct

    In PAT, the router should change the source port to a unique value. Both translations showing the same inside global port 80 indicates a problem.

  • The NAT pool is misconfigured because it uses the interface address.

    Why it's wrong here

    Using the interface address for PAT is valid.

  • The inside and outside interfaces are swapped.

    Why it's wrong here

    The statistics show correct interface assignment.

  • Static NAT is interfering with dynamic NAT.

    Why it's wrong here

    No static translations are present.

Visual reference

Inside (Private) PC-A 10.0.0.1 PC-B 10.0.0.2 NAT Router Outside (Public) 203.0.113.1 Inside Global Server PAT: many private IPs share one public IP via unique port numbers

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.