The answer is to apply the ACL narrow match principle, ensuring the rule targets only the specific destination and service. This design avoids overblocking by denying only the exact traffic intended—such as HTTP or HTTPS to a single web server—while leaving all other web destinations accessible. On the CCNA 200-301 v2 exam, this principle tests your understanding of precision in access control, often appearing in scenario-based questions where a broad deny statement (like denying an entire subnet) is a common trap. The key is to remember that ACLs process top-down, so a wide match early in the list can inadvertently block legitimate traffic. For a memory tip, think “sniper, not shotgun”—narrow your match to the specific IP and port, and always pair a deny with a subsequent permit any to confirm only the unwanted traffic is stopped.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: aCLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.. 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.
An administrator wants to prevent users from browsing to one specific web server while still allowing them to reach other web destinations. Which ACL design principle is most important here?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the narrowest possible match so only the intended traffic is denied.
The most important principle is to write the ACL as narrowly as possible so it matches only the unwanted traffic and does not overblock unrelated traffic. In practical terms, the rule should target the specific destination and service being denied rather than using a broader deny that unintentionally blocks other communication.
This is a precision-and-scope question. Good ACL design is as much about what you avoid blocking as what you intend to block.
Key principle: ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Use the narrowest possible match so only the intended traffic is denied.
Why this is correct
This is correct because precise ACL design reduces unintended side effects.
Related concept
ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
✗
Always deny all IP traffic to the destination subnet first.
Why it's wrong here
This is wrong because it may overblock beyond the requirement.
When this WOULD be correct
In a scenario where an administrator needs to implement a security policy that restricts all traffic to a specific subnet due to security concerns, such as isolating a compromised server, this option would be correct as it ensures no traffic reaches that subnet.
✗
Use a standard ACL because destination details never matter.
Why it's wrong here
This is wrong because destination detail matters greatly in this scenario.
When this WOULD be correct
In a scenario where an exam question asks about a network setup that only requires filtering based on source IP addresses, a standard ACL would be appropriate. For instance, if the question specifies that all traffic from a certain subnet should be denied regardless of the destination, then using a standard ACL would be the correct choice.
✗
Place the ACL only where no routing exists.
Why it's wrong here
This is wrong because the key issue here is match precision, not that rule.
When this WOULD be correct
In a scenario where a network design requires an ACL to be applied on a switch port that does not route traffic but still needs to control access to specific devices, placing the ACL at that point could be correct. For example, if the question specifies controlling access to a printer on a VLAN without routing, this option would apply.
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.
✓Use the narrowest possible match so only the intended traffic is denied.Correct answer▾
Why this is correct
This is correct because precise ACL design reduces unintended side effects.
✗Always deny all IP traffic to the destination subnet first.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because denying all IP traffic to the destination subnet would block all traffic to that subnet, not just the specific web server, which contradicts the requirement to allow access to other web destinations.
★ When this WOULD be the correct answer
In a scenario where an administrator needs to implement a security policy that restricts all traffic to a specific subnet due to security concerns, such as isolating a compromised server, this option would be correct as it ensures no traffic reaches that subnet.
Why candidates choose this
Candidates may find this option tempting because it suggests a comprehensive approach to security by blocking all traffic to a problematic subnet, which can seem like a straightforward method to enforce access control.
✗Use a standard ACL because destination details never matter.Wrong answer — click to see why▾
Why this is wrong here
Using a standard ACL ignores the importance of destination details, which are crucial for selectively denying access to one specific web server while allowing others. This approach would lead to broader access restrictions than intended.
★ When this WOULD be the correct answer
In a scenario where an exam question asks about a network setup that only requires filtering based on source IP addresses, a standard ACL would be appropriate. For instance, if the question specifies that all traffic from a certain subnet should be denied regardless of the destination, then using a standard ACL would be the correct choice.
Why candidates choose this
Candidates may be tempted by this option because standard ACLs are simpler and easier to implement, leading them to believe that they can effectively manage access without considering destination specifics.
✗Place the ACL only where no routing exists.Wrong answer — click to see why▾
Why this is wrong here
Placing the ACL only where no routing exists is incorrect because it does not address the requirement of selectively blocking traffic to a specific web server while allowing access to others. ACLs must be strategically placed to control traffic flow effectively based on routing paths.
★ When this WOULD be the correct answer
In a scenario where a network design requires an ACL to be applied on a switch port that does not route traffic but still needs to control access to specific devices, placing the ACL at that point could be correct. For example, if the question specifies controlling access to a printer on a VLAN without routing, this option would apply.
Why candidates choose this
Candidates might be tempted by this option because it suggests a simplistic approach to ACL placement, assuming that any location without routing would suffice for access control, which can seem intuitive without deeper understanding of ACL functionality.
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: answer the scenario, not the keyword
Avoid using broad deny statements that block more than necessary. Focus on precision by targeting both IP and port.
Trap categories for this question
Scenario analysis trap
This is wrong because destination detail matters greatly in this scenario.
Detailed technical explanation
How to think about this question
Access Control Lists (ACLs) are fundamental security tools in Cisco networking that filter traffic based on defined criteria such as source/destination IP addresses, protocols, and ports. They enable administrators to permit or deny specific traffic flows, controlling network access and enhancing security. In the context of web traffic, ACLs can be designed to block access to particular web servers by matching destination IP addresses and TCP port 80 or 443 for HTTP/HTTPS traffic.
The key to effective ACL design is precision: the ACL must narrowly match only the unwanted traffic to avoid disrupting legitimate communication. For example, denying traffic solely to the specific IP address of the targeted web server and the relevant TCP ports ensures that users can still access other web destinations. Overly broad ACLs, such as denying all traffic to a subnet or using standard ACLs that filter only by source IP, risk blocking more traffic than intended, causing network disruptions.
A common exam trap is to apply ACLs too broadly or in the wrong sequence, such as denying all traffic to a destination subnet or using standard ACLs that cannot filter by destination IP. This leads to unintended blocking of legitimate traffic and network outages. Understanding the Cisco ACL processing order and the importance of the narrowest match helps avoid these pitfalls and ensures ACLs enforce security policies without collateral damage.
KKey Concepts to Remember
ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
Extended ACLs allow filtering based on destination IP addresses and TCP/UDP ports, enabling precise control over web traffic access.
Using the narrowest possible ACL match prevents unintended blocking of legitimate traffic and maintains network usability.
Standard ACLs filter only by source IP address and cannot control traffic based on destination details, limiting their usefulness for web server blocking.
Applying ACLs at the correct interface and direction ensures that the intended traffic is filtered effectively without impacting unrelated flows.
Overly broad ACL rules, such as denying all traffic to a subnet, risk disrupting access to multiple services beyond the targeted web server.
Cisco ACLs process rules in sequential order, so placing specific deny statements before broader permits is essential for correct behavior.
ACL design must balance security enforcement with minimizing collateral impact on network communication to avoid operational issues.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
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 aCLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets., then practise related 200-301 questions on the same topic to reinforce the concept.
Network Services and Security — This question tests Network Services and Security — ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets..
What is the correct answer to this question?
The correct answer is: Use the narrowest possible match so only the intended traffic is denied. — The most important principle is to write the ACL as narrowly as possible so it matches only the unwanted traffic and does not overblock unrelated traffic. In practical terms, the rule should target the specific destination and service being denied rather than using a broader deny that unintentionally blocks other communication.
This is a precision-and-scope question. Good ACL design is as much about what you avoid blocking as what you intend to block.
What should I do if I get this 200-301 question wrong?
Review aCLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.