The answer is that an extended ACL is most strongly indicated when the policy must distinguish traffic by destination, protocol, or port. This is because a standard ACL can only filter based on the source IP address, making it far too limited for any rule that needs to differentiate between specific services like HTTP versus SSH or between different destination servers. On the CCNA 200-301 v2 exam, this concept tests your understanding of ACL capabilities and placement, often appearing in scenario-based questions where you must choose the right tool for the policy requirement. A common trap is assuming a standard ACL can handle port-level control, but it cannot—it only matches source addresses. For a quick memory tip, remember that extended ACLs are “extended” because they look deeper into the packet, checking the destination, protocol, and port, while standard ACLs are “standard” because they only check the source.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.. 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 standard ACL and an extended ACL are both available for a design. Which requirement most strongly indicates that an extended ACL is needed?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy must distinguish traffic by destination, protocol, or port.
An extended ACL is most strongly indicated when the policy must match not just on source address, but also on destination, protocol, or port information. In practical terms, if the requirement is something like “block HTTP but allow SSH” or “deny traffic to one server but not another,” a standard ACL is too limited because it mainly matches only the source. Option B (matching only one source subnet) can be done with a standard ACL, so it does not demand an extended ACL. Option C (placement near destination) is a guideline for standard ACLs, not a reason to choose an extended ACL. Option D (IPv6) is irrelevant because the scenario explicitly states both ACL types are available and standard ACLs do not exist for IPv6—this question is about IPv4 ACLs.
Key principle: Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.
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 policy must distinguish traffic by destination, protocol, or port.
Why this is correct
This is correct because those requirements need extended ACL granularity.
Related concept
Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.
✗
The policy needs to match only one source subnet.
Why it's wrong here
This is wrong because source-only matching is exactly where a standard ACL may be enough.
When this WOULD be correct
In a different scenario, if the exam question specifically states that the requirement is to implement a simple access control that only needs to allow or deny traffic from a single source subnet to a specific destination, then option B would be the correct choice.
✗
The ACL must be placed near the destination.
Why it's wrong here
This is wrong because placement guidance does not by itself determine the ACL type.
When this WOULD be correct
In a scenario where a question asks about the most effective ACL placement strategy for managing traffic flows to a specific server, stating that the ACL must be placed near the destination could be correct if the focus is on minimizing unnecessary traffic across the network.
✗
The network uses IPv6 instead of IPv4.
Why it's wrong here
This is wrong because the underlying need here is still about match detail, not that distinction.
When this WOULD be correct
In a different scenario, if the question asked about the necessity of ACLs for a network exclusively using IPv6, and the focus was on matching traffic based on IPv6-specific features, then this option could be correct, as extended ACLs are often used in IPv6 environments.
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 policy must distinguish traffic by destination, protocol, or port.Correct answer▾
Why this is correct
This is correct because those requirements need extended ACL granularity.
✗The policy needs to match only one source subnet.Wrong answer — click to see why▾
Why this is wrong here
Option B is incorrect because a standard ACL can effectively match a single source subnet without needing the additional capabilities of an extended ACL, which is designed for more complex filtering based on multiple criteria.
★ When this WOULD be the correct answer
In a different scenario, if the exam question specifically states that the requirement is to implement a simple access control that only needs to allow or deny traffic from a single source subnet to a specific destination, then option B would be the correct choice.
Why candidates choose this
Candidates may find this option tempting because it suggests a straightforward requirement that seems manageable with a standard ACL, leading them to overlook the need for more detailed traffic filtering capabilities that extended ACLs provide.
✗The ACL must be placed near the destination.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the requirement to place the ACL near the destination does not inherently necessitate an extended ACL; standard ACLs can also be effective in controlling traffic based on source addresses regardless of placement.
★ When this WOULD be the correct answer
In a scenario where a question asks about the most effective ACL placement strategy for managing traffic flows to a specific server, stating that the ACL must be placed near the destination could be correct if the focus is on minimizing unnecessary traffic across the network.
Why candidates choose this
Candidates may find this option tempting because they understand that placement can impact performance and security, leading them to believe that it is a critical factor in determining the type of ACL needed.
✗The network uses IPv6 instead of IPv4.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because the requirement for an extended ACL is based on the need to filter traffic by multiple criteria such as protocol or port, which is not addressed by simply matching one source subnet.
★ When this WOULD be the correct answer
In a different scenario, if the question asked about the necessity of ACLs for a network exclusively using IPv6, and the focus was on matching traffic based on IPv6-specific features, then this option could be correct, as extended ACLs are often used in IPv6 environments.
Why candidates choose this
Candidates may find this option tempting because they might associate IPv6 with advanced filtering needs, leading them to believe that it inherently requires extended ACLs, without considering the specific requirements of the question.
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
Remember that standard ACLs can only filter based on source IP addresses. If the requirement involves protocols or ports, think extended ACL.
Detailed technical explanation
How to think about this question
Access Control Lists (ACLs) are fundamental tools in Cisco networking used to filter traffic based on defined criteria. Standard ACLs filter traffic solely based on the source IP address, making them suitable for simple filtering tasks where only the origin of traffic matters. Extended ACLs provide much finer granularity by allowing filtering based on source and destination IP addresses, as well as protocol types (such as TCP, UDP, ICMP) and specific port numbers. This granularity enables network administrators to implement detailed security policies and traffic controls.
When deciding between a standard and an extended ACL, the key factor is the level of detail required in the filtering policy. If the policy requires distinguishing traffic by destination IP, protocol type, or port number—for example, blocking HTTP traffic while allowing SSH—an extended ACL is necessary. Standard ACLs cannot differentiate beyond source IP, so they are insufficient for policies needing protocol or port-based filtering. Cisco best practices also recommend placing extended ACLs close to the source of traffic to minimize unnecessary traffic on the network.
A common exam trap involves confusing ACL placement with ACL type. While extended ACLs are often placed near the source and standard ACLs near the destination, placement alone does not dictate the ACL type. Another pitfall is assuming IPv6 usage mandates extended ACLs; the deciding factor remains the filtering granularity. Practically, extended ACLs enable precise traffic control, which is essential for enforcing complex security policies in modern networks, making them indispensable when detailed traffic discrimination is required.
KKey Concepts to Remember
Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.
Extended ACLs filter traffic by source and destination IP addresses, protocol types, and port numbers, providing detailed traffic control.
The choice between standard and extended ACLs depends primarily on the required filtering granularity in the security policy.
Extended ACLs are necessary when the policy must differentiate traffic by destination IP, protocol, or port to enforce precise rules.
ACL placement near source or destination is a deployment best practice but does not determine whether to use standard or extended ACLs.
IPv6 networks require ACLs that support IPv6 addresses, but the filtering granularity rules for standard versus extended ACLs remain the same.
Misinterpreting ACL placement or IP version as the deciding factor for ACL type is a common exam trap.
Effective ACL design involves matching the ACL type to the filtering criteria to ensure proper traffic control and security enforcement.
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
Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.
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 standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port., 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 — Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port..
What is the correct answer to this question?
The correct answer is: The policy must distinguish traffic by destination, protocol, or port. — An extended ACL is most strongly indicated when the policy must match not just on source address, but also on destination, protocol, or port information. In practical terms, if the requirement is something like “block HTTP but allow SSH” or “deny traffic to one server but not another,” a standard ACL is too limited because it mainly matches only the source. Option B (matching only one source subnet) can be done with a standard ACL, so it does not demand an extended ACL. Option C (placement near destination) is a guideline for standard ACLs, not a reason to choose an extended ACL. Option D (IPv6) is irrelevant because the scenario explicitly states both ACL types are available and standard ACLs do not exist for IPv6—this question is about IPv4 ACLs.
What should I do if I get this 200-301 question wrong?
Review standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port., then practise related 200-301 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Standard ACLs filter traffic based solely on the source IP address and cannot distinguish by destination, protocol, or port.
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