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. 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.
Exhibit
R1# show running-config | section ip nat
ip nat inside source list 100 interface GigabitEthernet0/1
ip nat inside source static 192.168.1.10 203.0.113.10
!
R1# show running-config | section interface
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.0
ip nat outside
!
R1# show access-lists 100
Standard IP access list 100
10 permit 192.168.2.0 0.0.0.255
You are connected to R1. The inside network 192.168.1.0/24 must be able to reach the internet via PAT (overload) using the public IP 203.0.113.1 on interface GigabitEthernet0/1. Additionally, a web server at 192.168.1.10 must be reachable from the internet via static NAT to 203.0.113.10. The current configuration is not working. Identify and fix all issues.
R1# show running-config | section ip nat
ip nat inside source list 100 interface GigabitEthernet0/1
ip nat inside source static 192.168.1.10 203.0.113.10
!
R1# show running-config | section interface
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.0
ip nat outside
!
R1# show access-lists 100
Standard IP access list 100
10 permit 192.168.2.0 0.0.0.255
A
Change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.
This is correct because it fixes all three issues: the ACL now matches the correct inside network, the 'overload' keyword enables PAT, and verification confirms NAT is working.
B
Change ACL 100 to permit 192.168.1.0 0.0.0.255 and add the 'overload' keyword to the ip nat inside source list command.
Why wrong: This is incorrect because it omits the verification step; while the configuration changes are correct, verification is essential to confirm the fix works.
C
Add the 'overload' keyword to the ip nat inside source list command and verify with 'show ip nat translations'.
Why wrong: This is incorrect because it does not address the ACL issue; the ACL still permits the wrong network (192.168.2.0/24), so inside traffic from 192.168.1.0/24 will not be translated.
D
Change ACL 100 to permit 192.168.1.0 0.0.0.255 and verify with 'show ip nat translations'.
Why wrong: This is incorrect because it does not add the 'overload' keyword; without 'overload', PAT is not enabled, and only one inside host can use the public IP at a time.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.
The configuration has two issues: (1) ACL 100 permits 192.168.2.0/24 instead of 192.168.1.0/24, so the inside traffic is not matched for PAT. (2) The 'ip nat inside source list' command lacks the 'overload' keyword, preventing port address translation. The static NAT entry for the web server is correctly configured and does not depend on the ACL; it will work once the ACL is fixed. To resolve: change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.
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.
✓
Change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.
Why this is correct
This is correct because it fixes all three issues: the ACL now matches the correct inside network, the 'overload' keyword enables PAT, and verification confirms NAT is working.
Related concept
Static NAT maps one inside address to one outside address.
✗
Change ACL 100 to permit 192.168.1.0 0.0.0.255 and add the 'overload' keyword to the ip nat inside source list command.
Why it's wrong here
This is incorrect because it omits the verification step; while the configuration changes are correct, verification is essential to confirm the fix works.
✗
Add the 'overload' keyword to the ip nat inside source list command and verify with 'show ip nat translations'.
Why it's wrong here
This is incorrect because it does not address the ACL issue; the ACL still permits the wrong network (192.168.2.0/24), so inside traffic from 192.168.1.0/24 will not be translated.
✗
Change ACL 100 to permit 192.168.1.0 0.0.0.255 and verify with 'show ip nat translations'.
Why it's wrong here
This is incorrect because it does not add the 'overload' keyword; without 'overload', PAT is not enabled, and only one inside host can use the public IP at a time.
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.
✓Change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.Correct answer▾
Why this is correct
This is correct because it fixes all three issues: the ACL now matches the correct inside network, the 'overload' keyword enables PAT, and verification confirms NAT is working.
✗Change ACL 100 to permit 192.168.1.0 0.0.0.255 and add the 'overload' keyword to the ip nat inside source list command.Wrong answer — click to see why▾
Why this is wrong here
The answer fails to include the verification step, which is a critical part of troubleshooting and ensuring the configuration is applied correctly.
Why candidates choose this
Candidates might think only the configuration changes are needed, overlooking the importance of verifying with 'show ip nat translations'.
✗Add the 'overload' keyword to the ip nat inside source list command and verify with 'show ip nat translations'.Wrong answer — click to see why▾
Why this is wrong here
The ACL must match the correct inside network; without fixing it, PAT will not apply to the intended traffic.
Why candidates choose this
Candidates might focus only on the missing 'overload' keyword and forget that the ACL is also misconfigured.
✗Change ACL 100 to permit 192.168.1.0 0.0.0.255 and verify with 'show ip nat translations'.Wrong answer — click to see why▾
Why this is wrong here
The 'overload' keyword is essential for PAT; omitting it means the router will perform dynamic NAT without port translation, which is insufficient for multiple hosts.
Why candidates choose this
Candidates might think fixing the ACL is enough, not realizing that PAT requires the 'overload' keyword.
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: 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
Keyword trap
This is incorrect because it does not add the 'overload' keyword; without 'overload', PAT is not enabled, and only one inside host can use the public IP at a time.
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 200-301 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 200-301 NAT questions on configuration and troubleshooting.
Network Services and Security — This question tests Network Services and Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'. — The configuration has two issues: (1) ACL 100 permits 192.168.2.0/24 instead of 192.168.1.0/24, so the inside traffic is not matched for PAT. (2) The 'ip nat inside source list' command lacks the 'overload' keyword, preventing port address translation. The static NAT entry for the web server is correctly configured and does not depend on the ACL; it will work once the ACL is fixed. To resolve: change ACL 100 to permit 192.168.1.0 0.0.0.255, add 'overload' to the ip nat inside source list command, and verify with 'show ip nat translations'.
What should I do if I get this 200-301 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 200-301 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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