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. Internal hosts can access the internet, but traffic to a specific external server at 203.0.113.100 is being translated to a different source IP than expected. Router R1 shows: show ip nat translations: Pro Inside global Inside local Outside local Outside global --- 10.1.1.1 192.168.1.1 203.0.113.100 203.0.113.100. The server logs show connections from 10.1.1.1 instead of 203.0.113.1. 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
✓
The interface GigabitEthernet0/1 has a private IP address; configure a public IP or use a NAT pool.
The inside global address 10.1.1.1 is a private IP, indicating that the NAT is not translating to the public IP. This can happen if the interface GigabitEthernet0/1 has a private IP address or if there is a route-map that selects a different source. The correct fix is to ensure the interface has a public IP or use a NAT pool with public addresses.
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.
✓
The interface GigabitEthernet0/1 has a private IP address; configure a public IP or use a NAT pool.
Why this is correct
If the interface IP is private, NAT will use that private IP, causing the issue.
Related concept
Static NAT maps one inside address to one outside address.
✗
The access-list 100 is incorrectly matching traffic.
Why it's wrong here
The translation shows the correct inside local address, so ACL is working.
✗
The server is responding to the wrong IP due to asymmetric routing.
Why it's wrong here
The server sees the source IP as 10.1.1.1, which is the translated address.
✗
The NAT configuration is missing the 'overload' keyword.
Why it's wrong here
The configuration includes 'overload', and translations are occurring.
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.
Trap categories for this question
Command / output trap
The translation shows the correct inside local address, so ACL is working.
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: The interface GigabitEthernet0/1 has a private IP address; configure a public IP or use a NAT pool. — The inside global address 10.1.1.1 is a private IP, indicating that the NAT is not translating to the public IP. This can happen if the interface GigabitEthernet0/1 has a private IP address or if there is a route-map that selects a different source. The correct fix is to ensure the interface has a public IP or use a NAT pool with public addresses.
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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