The answer is that the 'ip nat inside source list' command identifies the traffic to be translated and specifies the translation method. This command works by referencing an access-list to match inside source addresses, then applying either dynamic or static NAT translation to those packets as they exit the inside interface. On the ENCOR 350-401 exam, this concept tests your understanding of how NAT policies are constructed and applied, often appearing in configuration or troubleshooting scenarios where you must distinguish between 'ip nat inside source list' (which selects traffic for translation) and 'ip nat inside source static' (which creates a fixed one-to-one mapping). A common trap is confusing the command with 'ip nat outside source list', which translates destination addresses instead. Remember the memory tip: "Inside list picks the source, outside list picks the destination" — this helps you quickly recall that the keyword 'inside' always refers to the source addresses being translated.
CCNP NAT and DHCP Practice Question
This 350-401 practice question tests your understanding of nat and dhcp. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
What is the purpose of the 'ip nat inside source list' command in Cisco IOS?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It identifies the traffic to be translated and the translation method.
This command specifies which inside source addresses (matched by an access-list) are to be translated using NAT.
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.
✗
It defines the inside interface for NAT.
Why it's wrong here
Incorrect. The inside interface is defined with 'ip nat inside' on the interface.
✓
It identifies the traffic to be translated and the translation method.
Why this is correct
Correct. The command ties an access-list to a NAT pool or interface for translation.
Related concept
Static NAT maps one inside address to one outside address.
✗
It filters inbound traffic before NAT is applied.
Why it's wrong here
Incorrect. The access-list is used to select source addresses for translation, not for filtering.
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
Incorrect. This command is for NAT, not DHCP.
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.
What to study next
Got this wrong? Here's your next step.
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 350-401 NAT questions on configuration and troubleshooting.
NAT and DHCP — This question tests NAT and DHCP — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: It identifies the traffic to be translated and the translation method. — This command specifies which inside source addresses (matched by an access-list) are to be translated using NAT.
What should I do if I get this 350-401 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 350-401 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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