- A
Reduce the NAT timeout values using ip nat translation timeout and ip nat translation tcp-timeout.
Shorter timeouts free up entries faster, preventing exhaustion.
- B
Increase the access-list 100 to include more internal hosts.
Why wrong: This would increase the number of translations, worsening the problem.
- C
Change the NAT to use a pool of public IPs instead of overload.
Why wrong: Using a pool would allow more translations but requires multiple public IPs and is not a direct fix for the timeout issue.
- D
Clear the NAT table with clear ip nat translation * periodically.
Why wrong: This is a temporary workaround, not a root cause fix.
Question 1,039 of 2,152
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.
Router R1 is configured with ip nat inside source list 100 interface GigabitEthernet0/1 overload. Users report that some websites load slowly or partially. Router R1 shows: show ip nat statistics: Total active translations: 65535 (0 static, 65535 dynamic; 65535 extended). The NAT pool is exhausted. What is the root cause?
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
✓
Reduce the NAT timeout values using ip nat translation timeout and ip nat translation tcp-timeout.
The NAT pool is exhausted with 65535 active translations, which is the maximum number of PAT entries (port numbers) available for a single public IP. This causes new or existing sessions to fail or load partially. Reducing NAT timeout values (e.g., ip nat translation timeout and ip nat translation tcp-timeout) frees port mappings faster, alleviating the exhaustion without requiring additional public IPs.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Reduce the NAT timeout values using ip nat translation timeout and ip nat translation tcp-timeout.
Why this is correct
Shorter timeouts free up entries faster, preventing exhaustion.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Increase the access-list 100 to include more internal hosts.
Why it's wrong here
This would increase the number of translations, worsening the problem.
- ✗
Change the NAT to use a pool of public IPs instead of overload.
Why it's wrong here
Using a pool would allow more translations but requires multiple public IPs and is not a direct fix for the timeout issue.
- ✗
Clear the NAT table with clear ip nat translation * periodically.
Why it's wrong here
This is a temporary workaround, not a root cause fix.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that adding more public IPs or clearing the NAT table is the primary fix, when in reality the root cause is port exhaustion due to long default timeouts, and the proper solution is to adjust timer values to reclaim ports faster.
Detailed technical explanation
How to think about this question
PAT (Port Address Translation) uses a single public IP and multiplexes up to 65,535 unique port numbers (0-65535, though 0-1023 are reserved). When all ports are consumed, no new translations can be created, causing connection timeouts or partial loads. The default TCP timeout is 86400 seconds (24 hours) and UDP timeout is 300 seconds; reducing these via ip nat translation tcp-timeout and ip nat translation udp-timeout (or the generic ip nat translation timeout) allows faster port reuse, especially for short-lived web sessions.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
NAT and PAT — This question tests NAT and PAT — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Reduce the NAT timeout values using ip nat translation timeout and ip nat translation tcp-timeout. — The NAT pool is exhausted with 65535 active translations, which is the maximum number of PAT entries (port numbers) available for a single public IP. This causes new or existing sessions to fail or load partially. Reducing NAT timeout values (e.g., ip nat translation timeout and ip nat translation tcp-timeout) frees port mappings faster, alleviating the exhaustion without requiring additional public IPs.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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