CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Network Topology
You are connected to R1 in a small office network. Configure PAT (NAT overload) so that hosts on the 192.168.1.0/24 LAN can access the Internet via the public IP 203.0.113.1 (the IP assigned to interface G0/0). Also configure a static NAT for the internal web server at 192.168.1.10 to the public IP 203.0.113.6. The current configuration has errors: the inside/outside interface assignments are swapped, the ACL for PAT does not match the inside subnet, and the PAT rule points to the wrong ACL. Fix all issues so that both PAT and static NAT work correctly.
R1# show running-config | section ip nat
ip nat inside source list 1 interface GigabitEthernet0/1 overload
ip nat inside source static tcp 192.168.1.10 80 203.0.113.6 80
!
ip nat inside source list 2 interface GigabitEthernet0/0 overload
!
interface GigabitEthernet0/0
ip address 203.0.113.1 255.255.255.248
ip nat inside
!
interface GigabitEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat outside
!
access-list 1 permit 192.168.2.0 0.0.0.255
access-list 2 permit 192.168.1.0 0.0.0.255
A
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
This correctly sets the outside interface (G0/0) and inside interface (G0/1), corrects the ACL to match the LAN subnet, and applies PAT using the correct ACL and outside interface. The static NAT is already correctly configured.
B
Configure G0/0 as inside, G0/1 as outside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/1 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why wrong: This is incorrect because the interface assignments are swapped: G0/0 (public) should be outside, not inside. PAT must be applied to the outside interface (G0/0), not G0/1.
C
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.2.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why wrong: This is incorrect because ACL 1 still permits the wrong subnet (192.168.2.0/24) instead of the correct inside subnet (192.168.1.0/24). PAT would not translate traffic from the LAN.
D
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 2 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why wrong: This is incorrect because the PAT command references ACL 2, but ACL 2 is not defined or does not match the inside subnet. The correct ACL is ACL 1 after modification.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
The main issues: (1) Interfaces were swapped — G0/0 (public) was inside and G0/1 (private) was outside. They should be reversed: G0/0 outside, G0/1 inside. (2) ACL 1 (used in the PAT command) permitted 192.168.2.0/24 instead of 192.168.1.0/24. (3) The PAT command for G0/0 used ACL 2, which was correct for the subnet but the interface was wrong. After fixing interface assignments and correcting ACL 1 to permit the inside subnet, the PAT command must use ACL 1 and the correct outside interface. The static NAT was correctly configured but needed the correct inside interface. The PAT translation uses the IP address of the outside interface (interface overload), so after fixing the configuration, inside hosts will be translated to 203.0.113.1, the primary IP of G0/0, not 203.0.113.5.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why this is correct
This correctly sets the outside interface (G0/0) and inside interface (G0/1), corrects the ACL to match the LAN subnet, and applies PAT using the correct ACL and outside interface. The static NAT is already correctly configured.
Configure G0/0 as inside, G0/1 as outside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/1 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why it's wrong here
This is incorrect because the interface assignments are swapped: G0/0 (public) should be outside, not inside. PAT must be applied to the outside interface (G0/0), not G0/1.
✗
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.2.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why it's wrong here
This is incorrect because ACL 1 still permits the wrong subnet (192.168.2.0/24) instead of the correct inside subnet (192.168.1.0/24). PAT would not translate traffic from the LAN.
✗
Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 2 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6
Why it's wrong here
This is incorrect because the PAT command references ACL 2, but ACL 2 is not defined or does not match the inside subnet. The correct ACL is ACL 1 after modification.
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.
✓Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6Correct answer▾
Why this is correct
This correctly sets the outside interface (G0/0) and inside interface (G0/1), corrects the ACL to match the LAN subnet, and applies PAT using the correct ACL and outside interface. The static NAT is already correctly configured.
✗Configure G0/0 as inside, G0/1 as outside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/1 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The inside/outside interface roles are reversed; PAT is applied to the wrong interface.
Why candidates choose this
Candidates might think the private interface should be inside and the public interface outside, but here they are swapped, and PAT is applied to the inside interface, which would not work.
✗Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.2.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The ACL does not match the inside network, so PAT will not be applied to LAN traffic.
Why candidates choose this
Candidates might overlook the ACL subnet mismatch, especially if they focus only on interface assignments and PAT command syntax.
✗Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 2 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The PAT command uses the wrong ACL number; it should use ACL 1, not ACL 2.
Why candidates choose this
Candidates might confuse the ACL numbers, especially if the original configuration had ACL 2 for PAT and they forget to change it to ACL 1 after correcting the ACL.
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: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Trap categories for this question
Command / output trap
This is incorrect because the PAT command references ACL 2, but ACL 2 is not defined or does not match the inside subnet. The correct ACL is ACL 1 after modification.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Network Services and Security — This question tests Network Services and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Configure G0/0 as outside, G0/1 as inside; modify ACL 1 to permit 192.168.1.0 0.0.0.255; apply ip nat inside source list 1 interface G0/0 overload; keep ip nat inside source static 192.168.1.10 203.0.113.6 — The main issues: (1) Interfaces were swapped — G0/0 (public) was inside and G0/1 (private) was outside. They should be reversed: G0/0 outside, G0/1 inside. (2) ACL 1 (used in the PAT command) permitted 192.168.2.0/24 instead of 192.168.1.0/24. (3) The PAT command for G0/0 used ACL 2, which was correct for the subnet but the interface was wrong. After fixing interface assignments and correcting ACL 1 to permit the inside subnet, the PAT command must use ACL 1 and the correct outside interface. The static NAT was correctly configured but needed the correct inside interface. The PAT translation uses the IP address of the outside interface (interface overload), so after fixing the configuration, inside hosts will be translated to 203.0.113.1, the primary IP of G0/0, not 203.0.113.5.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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