CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: nAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.. 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.
Exhibit
ip nat inside source list 10 interface g0/1
access-list 10 permit 10.10.10.0 0.0.0.255
G0/0 = inside
G0/1 = outside
Inside hosts can reach the internet only one at a time. What is the most likely NAT issue?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The NAT statement is missing the overload keyword
Without overload, dynamic NAT uses one public address per internal session mapping. PAT with overload is what lets many inside hosts share a single outside interface address at the same time.
Key principle: NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.
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 NAT statement is missing the overload keyword
Why this is correct
PAT requires overload when multiple hosts share one public address.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.
✗
The access list should deny the inside subnet
Why it's wrong here
That would stop translation altogether.
When this WOULD be correct
In a different scenario where the question states that internal hosts should not be allowed to access the internet at all, an access list denying the inside subnet would be the correct answer. This would be relevant in a security-focused question where restricting access is the goal.
✗
The inside and outside interface roles are reversed in the exhibit
Why it's wrong here
The symptom points more directly to missing overload.
When this WOULD be correct
In a different scenario, if a question presented a network diagram where the interfaces were explicitly labeled as inside and outside but were incorrectly configured in the NAT settings, then this option could be correct. For example, if the NAT configuration was applied to the outside interface instead of the inside, it would cause NAT to fail.
In a different exam scenario where the question specifies that NAT is being configured for public IP addresses only, and the context indicates that the use of private addresses is not allowed, this option could be correct. For example, if the question states that only public IPs are permitted for NAT, then option D would be valid.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The NAT statement is missing the overload keywordCorrect answer▾
Why this is correct
PAT requires overload when multiple hosts share one public address.
✗The access list should deny the inside subnetWrong answer — click to see why▾
Why this is wrong here
The access list in NAT configuration is used to identify which traffic should be translated, not to deny traffic. Denying the inside subnet would prevent any translation for those hosts, causing them to have no internet access at all, rather than allowing one at a time.
★ When this WOULD be the correct answer
In a different scenario where the question states that internal hosts should not be allowed to access the internet at all, an access list denying the inside subnet would be the correct answer. This would be relevant in a security-focused question where restricting access is the goal.
Why candidates choose this
A student might think that the access list controls which hosts can use NAT, and incorrectly assume that denying the subnet would limit access to one host at a time. However, the symptom of 'one at a time' is classic for missing overload, not access list misconfiguration.
✗The inside and outside interface roles are reversed in the exhibitWrong answer — click to see why▾
Why this is wrong here
If the inside and outside interfaces were reversed, internal hosts would not be able to reach the internet at all because the router would not translate their source addresses correctly. The symptom of 'one at a time' specifically indicates that translation is happening but only for one host, which is a PAT issue, not an interface role reversal.
★ When this WOULD be the correct answer
In a different scenario, if a question presented a network diagram where the interfaces were explicitly labeled as inside and outside but were incorrectly configured in the NAT settings, then this option could be correct. For example, if the NAT configuration was applied to the outside interface instead of the inside, it would cause NAT to fail.
Why candidates choose this
Students often confuse interface roles in NAT configuration. The symptom of limited connectivity might lead them to suspect a misconfiguration of inside/outside interfaces, but the 'one at a time' behavior is a hallmark of missing overload, not reversed interfaces.
✗NAT cannot be used with RFC1918 addressesWrong answer — click to see why▾
Why this is wrong here
NAT is specifically designed to translate RFC1918 private addresses to public addresses for internet access. Using NAT with RFC1918 addresses is a standard and common practice in virtually all enterprise networks.
★ When this WOULD be the correct answer
In a different exam scenario where the question specifies that NAT is being configured for public IP addresses only, and the context indicates that the use of private addresses is not allowed, this option could be correct. For example, if the question states that only public IPs are permitted for NAT, then option D would be valid.
Why candidates choose this
A student might recall that RFC1918 addresses are private and not routable on the internet, and mistakenly think that NAT cannot be used with them. However, NAT is the solution that allows these addresses to communicate with the internet.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that reversing the inside and outside interface roles causes the symptom of only one host accessing the internet at a time. While interface roles are critical for NAT operation, reversing them typically prevents translation altogether rather than limiting it to a single host. Another trap is thinking that the ACL should deny the inside subnet to fix the issue, but denying the inside subnet in the ACL stops all translations, causing no internet access. The real cause is missing the overload keyword, which is essential for PAT to allow multiple hosts to share one public IP simultaneously.
Detailed technical explanation
How to think about this question
Network Address Translation (NAT) is a fundamental IP service that allows multiple devices on a private network to access external networks using a limited number of public IP addresses. Dynamic NAT maps private IP addresses to a pool of public IP addresses on a one-to-one basis, which means each internal host requires a unique public IP for translation. Port Address Translation (PAT), also known as NAT overload, extends this by allowing multiple internal hosts to share a single public IP address by differentiating sessions using unique source port numbers.
In Cisco IOS, the NAT configuration must explicitly include the overload keyword in the NAT statement to enable PAT. Without overload, the router performs dynamic NAT without port translation, limiting simultaneous translations to the number of available public IP addresses in the pool. This restriction causes only one inside host to reach the internet at a time if only one public IP is configured. The overload keyword instructs the router to use port numbers to multiplex multiple inside hosts through a single public IP, enabling concurrent internet access.
A common exam trap is confusing the reversal of inside and outside interfaces or misconfiguring access control lists (ACLs) for NAT. While interface roles and ACLs are important, the symptom of only one host accessing the internet at a time directly points to missing the overload keyword. Practically, missing overload causes translation to fail for additional hosts once the single public IP is in use, whereas reversed interfaces or ACL errors typically prevent translation altogether or cause other connectivity issues.
KKey Concepts to Remember
NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.
Dynamic NAT without overload maps each inside host to a unique public IP address, limiting simultaneous translations.
PAT uses the overload keyword to allow multiple inside hosts to share one public IP by differentiating sessions with port numbers.
The overload keyword is required in Cisco NAT statements to enable PAT and support multiple concurrent inside hosts.
Inside and outside interface roles must be correctly assigned for NAT to function but do not cause single-host access issues alone.
Access control lists (ACLs) define which inside addresses are translated but denying the inside subnet stops translation entirely.
Without overload, only one inside host can access the internet at a time if only one public IP address is available.
Misunderstanding NAT configuration syntax and the role of overload is a common exam trap leading to connectivity failures.
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
NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.
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 200-301 question in full detail.
Review nAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks..
What is the correct answer to this question?
The correct answer is: The NAT statement is missing the overload keyword — Without overload, dynamic NAT uses one public address per internal session mapping. PAT with overload is what lets many inside hosts share a single outside interface address at the same time.
What should I do if I get this 200-301 question wrong?
Review nAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks., then practise related 200-301 questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
NAT allows private IP addresses to be translated to public IP addresses for internet access in Cisco networks.
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