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: extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.. 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.
What is the main reason extended ACLs are often placed closer to the source of the traffic being filtered?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
To stop unwanted traffic earlier and avoid carrying it farther through the network.
Extended ACLs are often placed close to the source so unwanted traffic is stopped earlier in the path. In practical terms, that conserves bandwidth and reduces unnecessary forwarding of traffic that will be denied anyway. Because extended ACLs can match more specific conditions such as source, destination, and protocol, they are especially useful early in the traffic path.
This is a standard ACL placement principle. The goal is not just security logic, but efficient use of the network as well.
Key principle: Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
To stop unwanted traffic earlier and avoid carrying it farther through the network.
Why this is correct
This is correct because extended ACLs are commonly placed near the source for efficiency and control.
Related concept
Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.
✗
Because extended ACLs can function only on source interfaces.
Why it's wrong here
This is wrong because extended ACLs are not limited to source interfaces only.
When this WOULD be correct
In a question that asks about the functionality of ACLs in a network where only source-based filtering is allowed, or in a scenario where the exam explicitly states that extended ACLs are limited to source interfaces due to specific device constraints, this option could be correct.
✗
Because standard ACLs must always be placed near the destination instead.
Why it's wrong here
This is misleading because the question is asking why extended ACLs are commonly placed near the source.
When this WOULD be correct
In a question specifically focused on the placement rules of standard ACLs, it could state that standard ACLs must be placed near the destination to effectively filter traffic based on source addresses, making this option correct in that context.
✗
Because ACL placement has no effect on network efficiency.
Why it's wrong here
This is wrong because earlier filtering can reduce unnecessary traffic movement.
When this WOULD be correct
In a different question that asks about the impact of ACL placement on network performance without specifying the type of ACL, option D could be correct if the context indicates that ACLs do not influence overall network efficiency in a specific scenario, such as a highly optimized network where all traffic is already filtered at the source.
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.
✓To stop unwanted traffic earlier and avoid carrying it farther through the network.Correct answer▾
Why this is correct
This is correct because extended ACLs are commonly placed near the source for efficiency and control.
✗Because extended ACLs can function only on source interfaces.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because extended ACLs can function on both source and destination interfaces, not just source interfaces. Their placement is based on filtering criteria rather than interface limitations.
★ When this WOULD be the correct answer
In a question that asks about the functionality of ACLs in a network where only source-based filtering is allowed, or in a scenario where the exam explicitly states that extended ACLs are limited to source interfaces due to specific device constraints, this option could be correct.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of ACL functionality, mistakenly believing that extended ACLs are restricted to source interfaces, which can lead to confusion about their operational capabilities.
✗Because standard ACLs must always be placed near the destination instead.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because standard ACLs can be placed at either the source or destination, depending on the filtering requirements, and are not restricted to only one location.
★ When this WOULD be the correct answer
In a question specifically focused on the placement rules of standard ACLs, it could state that standard ACLs must be placed near the destination to effectively filter traffic based on source addresses, making this option correct in that context.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of ACL types and their placement rules, leading them to confuse standard ACLs with extended ACLs and their respective filtering capabilities.
✗Because ACL placement has no effect on network efficiency.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because ACL placement does significantly affect network efficiency; placing ACLs closer to the source can reduce unnecessary traffic on the network. Extended ACLs are designed to filter traffic based on various criteria, and their placement is crucial for optimal performance.
★ When this WOULD be the correct answer
In a different question that asks about the impact of ACL placement on network performance without specifying the type of ACL, option D could be correct if the context indicates that ACLs do not influence overall network efficiency in a specific scenario, such as a highly optimized network where all traffic is already filtered at the source.
Why candidates choose this
Candidates may choose this option due to a common misconception that all ACLs operate uniformly and that their placement does not impact performance, leading to confusion about the specific roles of different types of ACLs.
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
A frequent exam trap is confusing the placement rules for extended ACLs with those for standard ACLs. Some candidates mistakenly think extended ACLs should be placed near the destination like standard ACLs or believe ACL placement does not affect network efficiency. This misunderstanding leads to incorrect answers because extended ACLs filter on multiple criteria and are most effective when placed near the traffic source to block unwanted packets early. Ignoring this principle can cause unnecessary traffic to consume bandwidth and processing resources downstream, which is a critical concept tested on the CCNA exam.
Detailed technical explanation
How to think about this question
Access Control Lists (ACLs) are fundamental Cisco security tools used to filter traffic based on defined criteria such as source and destination IP addresses, protocols, and ports. Extended ACLs provide granular control by allowing filtering based on multiple parameters, including source and destination IP addresses, protocol types (TCP, UDP, ICMP), and port numbers. This specificity enables network administrators to precisely control which traffic is permitted or denied, enhancing security and traffic management within a network.
The placement of extended ACLs is critical for network efficiency and security. Best practice dictates placing extended ACLs as close to the source of the traffic as possible. This approach stops unwanted traffic early, preventing it from traversing the network unnecessarily and consuming bandwidth. By filtering traffic near the source, the network reduces load on intermediate devices and links, improving overall performance and security posture. This contrasts with standard ACLs, which filter only by source IP and are typically placed near the destination to avoid inadvertently blocking legitimate traffic.
A common exam trap is misunderstanding ACL placement rules and confusing extended ACLs with standard ACLs. Candidates may incorrectly believe extended ACLs must be placed near the destination or that ACL placement does not impact network efficiency. In practice, placing extended ACLs near the source optimizes resource use and security. Misplacement can lead to inefficient traffic flow and potential security gaps. Understanding this principle is essential for both passing the CCNA exam and designing effective Cisco networks.
KKey Concepts to Remember
Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.
Placing extended ACLs near the source of traffic prevents unwanted packets from traversing the network, conserving bandwidth and reducing load on intermediate devices.
Standard ACLs filter only on source IP addresses and are typically placed near the destination to avoid blocking legitimate traffic prematurely.
Early filtering with extended ACLs improves network efficiency by reducing unnecessary forwarding of denied traffic across multiple network segments.
ACL placement directly impacts network performance and security, making strategic placement essential for effective traffic management.
Misplacing extended ACLs near the destination can lead to inefficient bandwidth use and increased processing on intermediate devices.
Cisco best practices recommend placing extended ACLs close to the traffic source to maximize filtering effectiveness and network resource optimization.
Understanding the difference in placement strategies between standard and extended ACLs is critical for CCNA exam success and practical network design.
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
Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.
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 extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control., 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 — Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control..
What is the correct answer to this question?
The correct answer is: To stop unwanted traffic earlier and avoid carrying it farther through the network. — Extended ACLs are often placed close to the source so unwanted traffic is stopped earlier in the path. In practical terms, that conserves bandwidth and reduces unnecessary forwarding of traffic that will be denied anyway. Because extended ACLs can match more specific conditions such as source, destination, and protocol, they are especially useful early in the traffic path.
This is a standard ACL placement principle. The goal is not just security logic, but efficient use of the network as well.
What should I do if I get this 200-301 question wrong?
Review extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Extended ACLs filter traffic based on multiple criteria including source IP, destination IP, protocol type, and port numbers, providing granular traffic control.
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