The answer is that PAT is failing to assign unique source ports, creating a port conflict that will break connectivity. When troubleshooting PAT port conflict in show ip nat translations, the key issue is that both inside hosts (10.0.0.10 and 10.0.0.11) share the same inside global address 192.0.2.10 and the same port 80, which violates how Port Address Translation operates. PAT must translate the source port to a unique high-numbered port for each session to distinguish between multiple internal hosts using the same global IP; identical ports mean the router cannot correctly return traffic to the correct internal host. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of NAT overload behavior and the importance of unique port allocation—a common trap is assuming two identical translations are fine because they show different outside ports. Remember the memory tip: "PAT needs a unique port per host, or return traffic gets lost."
300-410 NAT and PAT Practice Question
This 300-410 practice question tests your understanding of nat and pat. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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
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 inside hosts (10.0.0.10 and 10.0.0.11) both using the same inside global address 192.0.2.10 (the interface address) and the same port 80. This is a problem because PAT should assign unique source ports for each translation. Both translations show the same inside global port (80), which is incorrect; PAT should use different ports. This indicates a misconfiguration or a bug, as PAT normally changes the source port to a unique value. The correct answer is that PAT is not assigning unique ports, which will cause conflicts.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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.
Related concept
Static NAT maps one inside address to one outside address.
✗
The NAT pool is misconfigured because it uses the interface address.
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Trap categories for this question
Command / output trap
The statistics show correct interface assignment.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
NAT and PAT — This question tests NAT and PAT — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: PAT is not assigning unique source ports; both translations use port 80, which will cause conflicts. — The output shows two inside hosts (10.0.0.10 and 10.0.0.11) both using the same inside global address 192.0.2.10 (the interface address) and the same port 80. This is a problem because PAT should assign unique source ports for each translation. Both translations show the same inside global port (80), which is incorrect; PAT should use different ports. This indicates a misconfiguration or a bug, as PAT normally changes the source port to a unique value. The correct answer is that PAT is not assigning unique ports, which will cause conflicts.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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