Question 1,134 of 1,389
CCNA Network Services and Security Practice Question
Which two statements about standard and extended IPv4 ACLs are correct?
⚠ Common exam trap
A frequent exam trap is assuming that standard ACLs can filter traffic based on protocol types or Layer 4 ports, which they cannot. This misconception leads to incorrect placement decisions, such as placing standard ACLs near the source, which risks blocking legitimate traffic from other sources. Another trap is believing extended ACLs cannot filter ICMP traffic, but extended ACLs do support ICMP filtering. Misunderstanding these facts can cause confusion in both exam scenarios and real-world network design, resulting in incorrect ACL configurations and ineffective traffic control.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
A standard ACL matches only the source IPv4 address.
Standard ACLs match only the source IPv4 address, while extended ACLs can match protocol and source and destination details including ports. Because standard ACLs are less granular, they are usually placed closer to the destination. Extended ACLs are usually placed closer to the source.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A standard ACL matches only the source IPv4 address.
Why this is correct
A standard ACL evaluates packets using only the source IPv4 address in the IP header, ignoring destination, protocol, and port information. This coarse filtering means it cannot differentiate between services like HTTP and SSH on the same destination host. As a result, standard ACLs are typically placed near the destination to avoid inadvertently blocking traffic to other networks.
- ✓
An extended ACL can match protocol information and Layer 4 ports.
Why this is correct
Extended ACLs parse the IP header for protocol type, such as TCP, UDP, or ICMP, and can inspect Layer 4 source and destination ports for TCP and UDP traffic. This lets a single rule match a specific application, like permitting HTTP on port 80 while denying Telnet on port 23 to the same destination. Extended ACLs can also match additional parameters, including established connections and ICMP message types, giving them much finer control.
- ✗
A standard ACL is normally placed as close to the source as possible.
Why it's wrong here
Standard ACLs are actually placed as close to the destination as possible, not the source, because they filter only on the source address. If applied near the source, a deny statement could block all traffic from a host to any destination, including networks that should be permitted. Extended ACLs, with their ability to match protocol and ports, are the ones normally applied near the source to filter traffic before it consumes bandwidth.
When this WOULD be correct
In a question that asks about the placement of ACLs specifically for optimizing bandwidth usage or reducing load on upstream devices, option C could be correct if it stated that a standard ACL is placed close to the source to filter traffic before it enters the network.
- ✗
An extended ACL cannot filter ICMP traffic.
Why it's wrong here
Extended ACLs can definitely filter ICMP traffic because they can match the IP protocol field for ICMP (protocol number 1) and optionally specify ICMP message types and codes. For instance, an extended ACL can permit ICMP echo-request while denying echo-reply, selectively dropping ping responses but not the requests. This contradicts the claim that extended ACLs cannot filter ICMP.
When this WOULD be correct
In a different exam question asking specifically about the capabilities of standard ACLs versus extended ACLs in filtering traffic types, if the question stated that extended ACLs cannot filter ICMP, then option D would be correct, as it would align with the constraints of that specific scenario.
- ✗
Both ACL types require named ACL syntax to match traffic.
Why it's wrong here
Both numbered and named ACL syntax are valid for standard and extended ACLs in Cisco IOS; numbered ACLs use defined number ranges (standard 1-99 or 1300-1999, extended 100-199 or 2000-2699), while named ACLs use a descriptive word. The choice of syntax is based on administrative preference and the need for features like editing or removing individual entries, not on whether the ACL is standard or extended. Therefore, named ACL syntax is not required to match traffic with either type.
When this WOULD be correct
In a scenario where the exam question specifies that only named ACLs are allowed for configuration, and asks which types of ACLs can be used, option E would be correct if both standard and extended ACLs were defined to require named syntax exclusively.
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.
✓A standard ACL matches only the source IPv4 address.Correct answer▾
Why this is correct
A standard ACL evaluates packets using only the source IPv4 address in the IP header, ignoring destination, protocol, and port information. This coarse filtering means it cannot differentiate between services like HTTP and SSH on the same destination host. As a result, standard ACLs are typically placed near the destination to avoid inadvertently blocking traffic to other networks.
✗A standard ACL is normally placed as close to the source as possible.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because a standard ACL is typically placed as close to the destination as possible to minimize unnecessary traffic on the network, not at the source. The placement of ACLs is critical for effective traffic filtering.
★ When this WOULD be the correct answer
In a question that asks about the placement of ACLs specifically for optimizing bandwidth usage or reducing load on upstream devices, option C could be correct if it stated that a standard ACL is placed close to the source to filter traffic before it enters the network.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of ACL placement strategies, confusing the general practice of placing access lists with the specific type of ACL being discussed.
✗An extended ACL cannot filter ICMP traffic.Wrong answer — click to see why▾
Why this is wrong here
This option is wrong because extended ACLs can indeed filter ICMP traffic, as they are designed to match various protocols, including ICMP, based on both source and destination IP addresses and Layer 4 ports.
★ When this WOULD be the correct answer
In a different exam question asking specifically about the capabilities of standard ACLs versus extended ACLs in filtering traffic types, if the question stated that extended ACLs cannot filter ICMP, then option D would be correct, as it would align with the constraints of that specific scenario.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of the capabilities of extended ACLs, often confusing them with standard ACLs, which only filter based on source IP addresses and do not consider protocol types.
✗Both ACL types require named ACL syntax to match traffic.Wrong answer — click to see why▾
Why this is wrong here
This option is incorrect because standard and extended ACLs can be defined using both numbered and named syntax; named ACLs are not a requirement for either type. Therefore, stating that both require named ACL syntax is misleading.
★ When this WOULD be the correct answer
In a scenario where the exam question specifies that only named ACLs are allowed for configuration, and asks which types of ACLs can be used, option E would be correct if both standard and extended ACLs were defined to require named syntax exclusively.
Why candidates choose this
Candidates may find this option tempting because they might confuse the use of named ACLs with the general configuration of ACLs, leading them to believe that named syntax is a necessity for both types.
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?”
Visual reference
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Last reviewed: May 17, 2026
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