The answer is that the access list is missing a permit statement for TCP port 443, which causes HTTPS traffic to be dropped. This is correct because ACL 100 explicitly permits only TCP port 80 (HTTP) on line 10, while HTTPS relies on TCP port 443. Since no permit entry matches port 443, the traffic hits the explicit deny at line 20 or the implicit deny at the end of the ACL, resulting in a timeout. On the CCNA 200-301 v2 exam, this scenario tests your ability to read an ACL configuration and identify mismatched port numbers—a common trap where students assume “web traffic” covers both HTTP and HTTPS. The high match count on the deny statement is a key clue that legitimate traffic is being blocked. A useful memory tip: remember that HTTP and HTTPS are not interchangeable in ACLs—think of the “S” in HTTPS as standing for “Secure” and “Separate” port 443.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 access-lists
Standard IP access list 10
10 permit 192.168.1.0 0.0.0.255 (5 matches)
Extended IP access list 100
remark Allow HTTP to DMZ web servers
10 permit tcp any 192.168.1.0 0.0.0.255 eq www (234 matches)
remark Deny all other traffic and log
20 deny ip any any log (1356 matches)
Refer to the exhibit. An administrator is trying to access a web server in the DMZ at 192.168.1.10 using HTTPS, but the connection times out. The web server is confirmed to be running and listening on both port 80 and port 443. The administrator examines the access list configuration on the perimeter router. Based on the output of the show access-lists command, what is the most likely cause of the failure?
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.
R1# show access-lists
Standard IP access list 10
10 permit 192.168.1.0 0.0.0.255 (5 matches)
Extended IP access list 100
remark Allow HTTP to DMZ web servers
10 permit tcp any 192.168.1.0 0.0.0.255 eq www (234 matches)
remark Deny all other traffic and log
20 deny ip any any log (1356 matches)
A
The access list does not include a permit statement for TCP port 443.
The only permit entry for the 192.168.1.0/24 network is for 'eq www' (TCP port 80). No entry exists for port 443, so HTTPS traffic is denied by the explicit or implicit deny.
B
The access list is applied in the wrong direction on the interface.
Why wrong: The output of show access-lists does not provide any interface binding information. The command only shows the ACL entries and match counters; it gives no indication of direction or attachment.
C
The web server is not actually listening on TCP port 443, despite the configuration.
Why wrong: The scenario explicitly states that the web server is running and listening on both port 80 and port 443. The issue is purely an ACL filtering problem.
D
The 'deny ip any any log' statement at the end of the access list is blocking the HTTPS traffic, so it must be removed.
Why wrong: Removing the explicit deny statement would not help, because the default implicit deny-all still drops any traffic not explicitly permitted. The traffic must be allowed with a permit statement for port 443 before any deny line.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The access list does not include a permit statement for TCP port 443.
Line 10 of ACL 100 explicitly permits only TCP traffic with destination port 80 ('eq www'). HTTPS relies on TCP port 443, which is not matched by any permit entry. Consequently, HTTPS traffic from any source to any host in 192.168.1.0/24 hits the explicit deny at line 20 (or the implicit deny) and is dropped. The high match count on the deny statement (1356) confirms that traffic other than HTTP is being blocked, including HTTPS.
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.
✓
The access list does not include a permit statement for TCP port 443.
Why this is correct
The only permit entry for the 192.168.1.0/24 network is for 'eq www' (TCP port 80). No entry exists for port 443, so HTTPS traffic is denied by the explicit or implicit deny.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Static NAT maps one inside address to one outside address.
✗
The access list is applied in the wrong direction on the interface.
Why it's wrong here
The output of show access-lists does not provide any interface binding information. The command only shows the ACL entries and match counters; it gives no indication of direction or attachment.
✗
The web server is not actually listening on TCP port 443, despite the configuration.
Why it's wrong here
The scenario explicitly states that the web server is running and listening on both port 80 and port 443. The issue is purely an ACL filtering problem.
✗
The 'deny ip any any log' statement at the end of the access list is blocking the HTTPS traffic, so it must be removed.
Why it's wrong here
Removing the explicit deny statement would not help, because the default implicit deny-all still drops any traffic not explicitly permitted. The traffic must be allowed with a permit statement for port 443 before any deny line.
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 access list does not include a permit statement for TCP port 443.Correct answer▾
Why this is correct
The only permit entry for the 192.168.1.0/24 network is for 'eq www' (TCP port 80). No entry exists for port 443, so HTTPS traffic is denied by the explicit or implicit deny.
✗The access list is applied in the wrong direction on the interface.Wrong answer — click to see why▾
Why this is wrong here
Candidates may assume the ACL is not applied correctly, but without interface details this conclusion cannot be drawn from the given output.
✗The web server is not actually listening on TCP port 443, despite the configuration.Wrong answer — click to see why▾
Why this is wrong here
Candidates might blame the server configuration rather than the network ACL, but the question stem provides the server state to rule this out.
✗The 'deny ip any any log' statement at the end of the access list is blocking the HTTPS traffic, so it must be removed.Wrong answer — click to see why▾
Why this is wrong here
This is a common misconception: the explicit deny is not the root cause; the missing permit is the real issue. Removing the deny without adding a permit for HTTPS would still result in the traffic being blocked by the implicit deny.
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
Command / output trap
The output of show access-lists does not provide any interface binding information. The command only shows the ACL entries and match counters; it gives no indication of direction or attachment.
Scenario analysis trap
The scenario explicitly states that the web server is running and listening on both port 80 and port 443. The issue is purely an ACL filtering problem.
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: The access list does not include a permit statement for TCP port 443. — Line 10 of ACL 100 explicitly permits only TCP traffic with destination port 80 ('eq www'). HTTPS relies on TCP port 443, which is not matched by any permit entry. Consequently, HTTPS traffic from any source to any host in 192.168.1.0/24 hits the explicit deny at line 20 (or the implicit deny) and is dropped. The high match count on the deny statement (1356) confirms that traffic other than HTTP is being blocked, including HTTPS.
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.
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?
Static NAT maps one inside address to one outside address.
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