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.
Exhibit
R1# show running-config | section ip nat
ip nat inside source list 100 interface GigabitEthernet0/1
ip nat inside source static tcp 192.168.1.100 80 interface GigabitEthernet0/1 80
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.248
ip nat inside
!
access-list 100 permit ip 192.168.2.0 0.0.0.255 any
You are connected to R1. The internal network 192.168.1.0/24 must be able to access the Internet via PAT (NAT overload) using the outside interface G0/1 with IP 203.0.113.1. Additionally, a web server at 192.168.1.100 must be reachable from the Internet via static NAT to the same outside interface. The current configuration has errors. Correct the NAT configuration so that inside hosts can browse the web and the server is reachable from outside.
R1# show running-config | section ip nat
ip nat inside source list 100 interface GigabitEthernet0/1
ip nat inside source static tcp 192.168.1.100 80 interface GigabitEthernet0/1 80
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.248
ip nat inside
!
access-list 100 permit ip 192.168.2.0 0.0.0.255 any
A
Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
This corrects all three errors: G0/1 must be 'ip nat outside' for PAT to work, 'overload' enables many-to-one translation, and ACL 100 must match the correct inside subnet 192.168.1.0/24.
B
Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and change ACL 100 to permit 192.168.2.0 0.0.0.255
Why wrong: This is incorrect because ACL 100 still permits the wrong subnet (192.168.2.0/24) instead of the actual inside subnet 192.168.1.0/24, so traffic from 192.168.1.0/24 will not be translated.
C
Change interface G0/1 to 'ip nat outside', remove the 'overload' keyword from the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
Why wrong: This is incorrect because removing 'overload' disables PAT; without 'overload', only one-to-one translation occurs, which is insufficient for multiple internal hosts to share the single outside IP.
D
Change interface G0/1 to 'ip nat inside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
Why wrong: This is incorrect because G0/1 must be 'ip nat outside', not 'ip nat inside'. With both interfaces as 'inside', NAT translations will not occur for traffic exiting G0/1.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
The configuration had three issues: (1) Interface G0/1 was incorrectly configured as 'ip nat inside' instead of 'ip nat outside' — this prevents translation as both interfaces are inside. (2) The NAT overload keyword was missing on the dynamic PAT rule — without 'overload', only one-to-one translation occurs. (3) ACL 100 was matching 192.168.2.0/24 instead of the actual inside subnet 192.168.1.0/24, so traffic from the correct subnet was not translated. Correcting these allows inside hosts to PAT to the outside IP and the static NAT to function properly.
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.
✓
Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
Why this is correct
This corrects all three errors: G0/1 must be 'ip nat outside' for PAT to work, 'overload' enables many-to-one translation, and ACL 100 must match the correct inside subnet 192.168.1.0/24.
Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and change ACL 100 to permit 192.168.2.0 0.0.0.255
Why it's wrong here
This is incorrect because ACL 100 still permits the wrong subnet (192.168.2.0/24) instead of the actual inside subnet 192.168.1.0/24, so traffic from 192.168.1.0/24 will not be translated.
✗
Change interface G0/1 to 'ip nat outside', remove the 'overload' keyword from the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
Why it's wrong here
This is incorrect because removing 'overload' disables PAT; without 'overload', only one-to-one translation occurs, which is insufficient for multiple internal hosts to share the single outside IP.
✗
Change interface G0/1 to 'ip nat inside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255
Why it's wrong here
This is incorrect because G0/1 must be 'ip nat outside', not 'ip nat inside'. With both interfaces as 'inside', NAT translations will not occur for traffic exiting G0/1.
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 interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255Correct answer▾
Why this is correct
This corrects all three errors: G0/1 must be 'ip nat outside' for PAT to work, 'overload' enables many-to-one translation, and ACL 100 must match the correct inside subnet 192.168.1.0/24.
✗Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and change ACL 100 to permit 192.168.2.0 0.0.0.255Wrong answer — click to see why▾
Why this is wrong here
The ACL must match the source subnet of the inside hosts that need translation; using 192.168.2.0/24 does not match 192.168.1.0/24.
Why candidates choose this
Candidates might misread the subnet or think the ACL is correct if they confuse the two subnets.
✗Change interface G0/1 to 'ip nat outside', remove the 'overload' keyword from the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255Wrong answer — click to see why▾
Why this is wrong here
The 'overload' keyword is essential for PAT; omitting it means only one inside host can use the outside IP at a time.
Why candidates choose this
Candidates might think 'overload' is optional or confuse it with static NAT, not realizing PAT requires it.
✗Change interface G0/1 to 'ip nat inside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255Wrong answer — click to see why▾
Why this is wrong here
NAT requires one interface to be 'inside' and the other 'outside'; having both as 'inside' prevents translation of outbound traffic.
Why candidates choose this
Candidates might think the outside interface should be 'inside' because it connects to the internal network, or they may confuse the direction of NAT.
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: Change interface G0/1 to 'ip nat outside', add 'overload' to the dynamic NAT rule, and correct ACL 100 to permit 192.168.1.0 0.0.0.255 — The configuration had three issues: (1) Interface G0/1 was incorrectly configured as 'ip nat inside' instead of 'ip nat outside' — this prevents translation as both interfaces are inside. (2) The NAT overload keyword was missing on the dynamic PAT rule — without 'overload', only one-to-one translation occurs. (3) ACL 100 was matching 192.168.2.0/24 instead of the actual inside subnet 192.168.1.0/24, so traffic from the correct subnet was not translated. Correcting these allows inside hosts to PAT to the outside IP and the static NAT to function properly.
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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