- A
The router's HTTP inspection rule is blocking outbound TCP port 80.
Why wrong: HTTP inspection is not required for basic PAT operation; a missing inspection policy does not block HTTP translation.
- B
The NAT access list still permits 192.168.0.0/24 and does not match the new 10.0.0.0/24 addresses.
Because the ACL that defines inside local addresses for PAT was never updated after renumbering, no dynamic translations are created for HTTP sourced from 10.0.0.0/24.
- C
The outside interface access list is blocking TCP packets from the new 10.0.0.0/24 subnet.
Why wrong: While an outbound ACL could block HTTP while allowing ICMP, the scenario’s emphasis on the renumbering and the PAT ACL makes the NAT mismatch a more probable root cause.
- D
The default route has been changed to point to the wrong next-hop address, causing only HTTP packets to be dropped.
Why wrong: A default route problem would affect all outbound traffic, including ICMP. Since ping succeeds, the default route is not the cause.
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.
A technician is troubleshooting an issue where internal hosts can successfully ping internet addresses but cannot establish HTTP sessions. The router is configured with PAT (overload) and uses an access list to define the inside local addresses. Recently, the internal network was renumbered from 192.168.0.0/24 to 10.0.0.0/24. What is the most likely cause?
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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The NAT access list still permits 192.168.0.0/24 and does not match the new 10.0.0.0/24 addresses.
PAT translates private addresses to a single public IP by matching the source against a NAT access list. The ACL permits only 192.168.0.0/24, so packets from the new 10.0.0.0/24 addresses are not translated. ICMP may still succeed due to an existing static NAT entry for ICMP echo or a separate rule, but HTTP requires new dynamic translations that the ACL blocks. The other options are plausible but do not align as directly with the recent renumbering and the configured NAT ACL.
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.
- ✗
The router's HTTP inspection rule is blocking outbound TCP port 80.
- ✓
The NAT access list still permits 192.168.0.0/24 and does not match the new 10.0.0.0/24 addresses.
Why this is correct
Because the ACL that defines inside local addresses for PAT was never updated after renumbering, no dynamic translations are created for HTTP sourced from 10.0.0.0/24.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
- ✗
The outside interface access list is blocking TCP packets from the new 10.0.0.0/24 subnet.
- ✗
The default route has been changed to point to the wrong next-hop address, causing only HTTP packets to be dropped.
Why it's wrong here
A default route problem would affect all outbound traffic, including ICMP. Since ping succeeds, the default route is not the cause.
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 access list still permits 192.168.0.0/24 and does not match the new 10.0.0.0/24 addresses.Correct answer▾
Why this is correct
Because the ACL that defines inside local addresses for PAT was never updated after renumbering, no dynamic translations are created for HTTP sourced from 10.0.0.0/24.
✗The router's HTTP inspection rule is blocking outbound TCP port 80.Wrong answer — click to see why▾
Why this is wrong here
Candidates may confuse security inspection with NAT translation, assuming that a protocol‑specific inspection is needed for HTTP.
✗The outside interface access list is blocking TCP packets from the new 10.0.0.0/24 subnet.Wrong answer — click to see why▾
Why this is wrong here
Tempting because an ACL could selectively block TCP; however, the question provides context about the renumbering, which directly points to the NAT configuration.
✗The default route has been changed to point to the wrong next-hop address, causing only HTTP packets to be dropped.Wrong answer — click to see why▾
Why this is wrong here
Candidates may assume that different protocols might take different paths, but a single default route applies uniformly to all IP traffic.
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
Scenario analysis trap
While an outbound ACL could block HTTP while allowing ICMP, the scenario’s emphasis on the renumbering and the PAT ACL makes the NAT mismatch a more probable root cause.
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.
What to study next
Got this wrong? Here's your next step.
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.
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FAQ
Questions learners often ask
What does this 200-301 question test?
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: The NAT access list still permits 192.168.0.0/24 and does not match the new 10.0.0.0/24 addresses. — PAT translates private addresses to a single public IP by matching the source against a NAT access list. The ACL permits only 192.168.0.0/24, so packets from the new 10.0.0.0/24 addresses are not translated. ICMP may still succeed due to an existing static NAT entry for ICMP echo or a separate rule, but HTTP requires new dynamic translations that the ACL blocks. The other options are plausible but do not align as directly with the recent renumbering and the configured NAT ACL.
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.
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?
CIDR notation defines the prefix length.
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Last reviewed: Jun 14, 2026
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
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