Quick Answer
The correct answer is to place an extended ACL as close to the source as practical. This positioning is critical because extended ACLs evaluate traffic based on source and destination IP addresses, ports, and protocols, allowing them to filter unwanted packets immediately at the edge of the source network. By stopping malicious or unnecessary traffic early, you conserve bandwidth and device processing resources across the entire path to the destination. On the CCNA 200-301 v2 exam, this concept tests your understanding of ACL efficiency versus standard ACLs, which are placed near the destination. A common trap is confusing extended ACL placement with standard ACL placement—remember, extended ACLs filter more granularly, so they belong close to the source to prevent wasted transit. A helpful memory tip is “Extended, early; Standard, late,” reinforcing that extended ACLs stop traffic sooner to protect network resources.
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 source and destination IP addresses as well as Layer 4 protocol information, enabling precise 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.
As a general rule, where should an extended ACL be placed?
As close to the source as practical
Correct. This is the common placement guideline.
As close to the destination as possible in all cases
Why wrong: That guidance is more often associated with standard ACLs.
Only on the default gateway
Why wrong: Extended ACLs are not limited to default gateways.
Only on WAN interfaces
Why wrong: They are not limited to WAN interfaces.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
As close to the source as practical
Extended ACLs are commonly placed near the source to stop unwanted traffic earlier and conserve bandwidth and device resources.
Key principle: Extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
As close to the source as practical
Why this is correct
Correct. This is the common placement guideline.
Related concept
Extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control.
As close to the destination as possible in all cases
Why it's wrong here
That guidance is more often associated with standard ACLs.
When this WOULD be correct
In a scenario where the question specifies that the network is highly segmented and traffic must be controlled at the destination for compliance reasons, placing an extended ACL close to the destination might be the best approach to enforce specific access policies for that segment.
Only on the default gateway
Why it's wrong here
Extended ACLs are not limited to default gateways.
When this WOULD be correct
In a scenario where a question specifies that all traffic must be filtered at the default gateway due to a specific network design or security policy, stating that extended ACLs should only be on the default gateway could be correct. For example, if the question indicates that the network is small and all traffic must pass through the gateway, this option would apply.
Only on WAN interfaces
Why it's wrong here
They are not limited to WAN interfaces.
When this WOULD be correct
In a scenario where the exam question specifies that the network design requires strict control over traffic entering and leaving a WAN connection, placing an extended ACL only on WAN interfaces could be the correct answer. This would apply in a situation where all traffic must be filtered at the edge of the network for security compliance.
Option-by-option analysis
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.
Why this is correct
Correct. This is the common placement guideline.
Why this is wrong here
Placing an extended ACL as close to the destination can lead to unnecessary traffic being processed by intermediate devices, which is inefficient. Extended ACLs are designed to filter traffic based on source and destination, so positioning them closer to the source enhances performance and security.
★ When this WOULD be the correct answer
In a scenario where the question specifies that the network is highly segmented and traffic must be controlled at the destination for compliance reasons, placing an extended ACL close to the destination might be the best approach to enforce specific access policies for that segment.
Why candidates choose this
Candidates may choose this option because they associate ACLs with controlling access at the endpoint, believing that filtering at the destination is a more secure practice without considering the efficiency of traffic management.
Why this is wrong here
This option is incorrect because placing an extended ACL only on the default gateway limits its effectiveness in controlling traffic originating from various sources across the network. Extended ACLs should be strategically placed closer to the source to filter traffic before it reaches the destination.
★ When this WOULD be the correct answer
In a scenario where a question specifies that all traffic must be filtered at the default gateway due to a specific network design or security policy, stating that extended ACLs should only be on the default gateway could be correct. For example, if the question indicates that the network is small and all traffic must pass through the gateway, this option would apply.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of ACL placement principles, believing that centralizing control at the default gateway simplifies management and security, without considering the broader implications of traffic flow.
Why this is wrong here
Placing an extended ACL only on WAN interfaces can lead to inefficient traffic filtering, as it may not adequately control traffic originating from internal sources. Extended ACLs should ideally be positioned close to the source to effectively manage traffic before it reaches the destination.
★ When this WOULD be the correct answer
In a scenario where the exam question specifies that the network design requires strict control over traffic entering and leaving a WAN connection, placing an extended ACL only on WAN interfaces could be the correct answer. This would apply in a situation where all traffic must be filtered at the edge of the network for security compliance.
Why candidates choose this
Candidates may find this option tempting because they associate WAN interfaces with external traffic control, leading them to believe that filtering at this point is sufficient for managing network security.
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
Remember that extended ACLs should be placed near the source, not the destination or core, to effectively manage traffic.
Detailed technical explanation
Access Control Lists (ACLs) are fundamental security tools in Cisco networking used to filter traffic based on defined criteria such as source/destination IP addresses, protocols, and ports. Extended ACLs provide granular control by filtering traffic based on multiple parameters, including source and destination IP addresses and Layer 4 protocols, enabling precise traffic filtering beyond what standard ACLs offer. The general rule for placing extended ACLs is to position them as close to the source of the traffic as practical. This placement ensures that unwanted traffic is blocked early in the network path, conserving bandwidth and reducing unnecessary processing on intermediate devices. By filtering traffic near the source, the network avoids carrying unwanted packets across multiple links, which optimizes resource utilization and enhances overall network performance. A common exam trap is to confuse the placement of extended ACLs with that of standard ACLs. Standard ACLs are typically placed near the destination because they filter only on source IP addresses, which can inadvertently block legitimate traffic if placed near the source. Extended ACLs, however, filter on both source and destination, allowing safe placement near the source. Understanding this distinction is critical for both exam success and practical network security design.
Key takeaway
Extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control.
Real-world example
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
Review extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Services and Security — This question tests Network Services and Security — Extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control..
The correct answer is: As close to the source as practical — Extended ACLs are commonly placed near the source to stop unwanted traffic earlier and conserve bandwidth and device resources.
Review extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control., then practise related 200-301 questions on the same topic to reinforce the concept.
Extended ACLs filter traffic based on source and destination IP addresses as well as Layer 4 protocol information, enabling precise traffic control.
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Last reviewed: Apr 12, 2026
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