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. The inside network 192.168.1.0/24 must be able to access the internet using PAT (NAT overload) with the outside interface G0/1 IP 203.0.113.1. Additionally, the internal server at 192.168.1.10 must be reachable from the internet via static NAT to 203.0.113.10. The current configuration is incomplete and contains errors. Identify and fix all issues so that both PAT and static NAT work correctly.
R1# show running-config | section ip nat
ip nat pool GLOBAL 203.0.113.1 203.0.113.1 netmask 255.255.255.0
ip nat inside source list 1 pool GLOBAL
ip nat inside source static tcp 192.168.1.10 80 203.0.113.10 80
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat outside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.0
ip nat inside
!
access-list 1 permit 192.168.2.0 0.0.0.255
A
Swap ip nat inside/outside on interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.
This option correctly identifies all three faults: the inside/outside interface assignments were reversed, the PAT command lacked the 'overload' keyword, and ACL 1 permitted the wrong subnet. Fixing these ensures both PAT and static NAT function properly.
B
Change the static NAT inside address to 192.168.1.1 and add 'overload' to the dynamic NAT rule.
Why wrong: This is incorrect because the static NAT inside address (192.168.1.10) is correct as per the requirement. Changing it to 192.168.1.1 would break the requirement. Additionally, only one fault (missing 'overload') is addressed, ignoring the interface and ACL issues.
C
Remove the static NAT configuration and rely solely on PAT for the server.
Why wrong: This is incorrect because the requirement explicitly states the server must be reachable from the internet via static NAT. Removing static NAT would prevent inbound access to the server.
D
Add the 'overload' keyword to the dynamic NAT rule and correct ACL 1 to permit 192.168.1.0/24.
Why wrong: This is incorrect because it fails to address the swapped inside/outside interface assignments. Without correcting the interface NAT directions, both PAT and static NAT will not work.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Swap ip nat inside/outside on interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.
The configuration had multiple faults: 1) Inside/outside interfaces were swapped – G0/0 (LAN) should be inside, G0/1 (WAN) should be outside. 2) The PAT command was missing the 'overload' keyword. 3) ACL 1 permitted the wrong subnet (192.168.2.0/24 instead of 192.168.1.0/24). 4) The static NAT configuration was correct, but the interface misconfiguration prevented it from working. Fixes: swap ip nat inside/outside on the interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.
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.
✓
Swap ip nat inside/outside on interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.
Why this is correct
This option correctly identifies all three faults: the inside/outside interface assignments were reversed, the PAT command lacked the 'overload' keyword, and ACL 1 permitted the wrong subnet. Fixing these ensures both PAT and static NAT function properly.
Change the static NAT inside address to 192.168.1.1 and add 'overload' to the dynamic NAT rule.
Why it's wrong here
This is incorrect because the static NAT inside address (192.168.1.10) is correct as per the requirement. Changing it to 192.168.1.1 would break the requirement. Additionally, only one fault (missing 'overload') is addressed, ignoring the interface and ACL issues.
✗
Remove the static NAT configuration and rely solely on PAT for the server.
Why it's wrong here
This is incorrect because the requirement explicitly states the server must be reachable from the internet via static NAT. Removing static NAT would prevent inbound access to the server.
✗
Add the 'overload' keyword to the dynamic NAT rule and correct ACL 1 to permit 192.168.1.0/24.
Why it's wrong here
This is incorrect because it fails to address the swapped inside/outside interface assignments. Without correcting the interface NAT directions, both PAT and static NAT will not work.
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.
✓Swap ip nat inside/outside on interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.Correct answer▾
Why this is correct
This option correctly identifies all three faults: the inside/outside interface assignments were reversed, the PAT command lacked the 'overload' keyword, and ACL 1 permitted the wrong subnet. Fixing these ensures both PAT and static NAT function properly.
✗Change the static NAT inside address to 192.168.1.1 and add 'overload' to the dynamic NAT rule.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the static NAT inside address is already correct; altering it is unnecessary and incorrect.
Why candidates choose this
Candidates might think the server's inside address should be the default gateway (192.168.1.1) or confuse it with the inside global address.
✗Remove the static NAT configuration and rely solely on PAT for the server.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that static NAT is required for inbound access; PAT alone cannot provide a fixed public-to-private mapping.
Why candidates choose this
Candidates might think PAT can handle all traffic, but PAT only translates multiple private addresses to a single public address and does not allow unsolicited inbound connections without additional configuration.
✗Add the 'overload' keyword to the dynamic NAT rule and correct ACL 1 to permit 192.168.1.0/24.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that interface NAT direction is fundamental; if inside/outside are reversed, NAT translations will not be applied correctly.
Why candidates choose this
Candidates might focus on the ACL and PAT keyword but overlook the interface configuration, which is a common misconfiguration in NAT setups.
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.
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: Swap ip nat inside/outside on interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24. — The configuration had multiple faults: 1) Inside/outside interfaces were swapped – G0/0 (LAN) should be inside, G0/1 (WAN) should be outside. 2) The PAT command was missing the 'overload' keyword. 3) ACL 1 permitted the wrong subnet (192.168.2.0/24 instead of 192.168.1.0/24). 4) The static NAT configuration was correct, but the interface misconfiguration prevented it from working. Fixes: swap ip nat inside/outside on the interfaces, add 'overload' to the dynamic NAT rule, and correct ACL 1 to permit 192.168.1.0/24.
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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