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 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 translation table is full (65535 entries, the maximum for PAT), meaning no new translations can be created. This can cause partial loading as some connections fail. The root cause is likely that NAT timeouts are too long (default 24 hours for TCP) or there is a DoS attack generating many connections. The correct fix is to reduce timeouts or increase the number of available ports by using multiple public IPs.
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.
✓
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
Static NAT maps one inside address to one outside address.
✗
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: 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.
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: Reduce the NAT timeout values using ip nat translation timeout and ip nat translation tcp-timeout. — The NAT translation table is full (65535 entries, the maximum for PAT), meaning no new translations can be created. This can cause partial loading as some connections fail. The root cause is likely that NAT timeouts are too long (default 24 hours for TCP) or there is a DoS attack generating many connections. The correct fix is to reduce timeouts or increase the number of available ports by using multiple public IPs.
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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