The answer is source and destination IP addresses, protocol, and port numbers. Extended ACLs operate at both Layer 3 and Layer 4 of the OSI model, which allows them to match on these four specific fields for granular traffic filtering, unlike standard ACLs that only match on source IP. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your ability to configure precise traffic control for routing protocols and network services, often appearing in scenario-based questions where you must choose the correct extended ACL entry. A common trap is forgetting that protocol matching (e.g., TCP, UDP, ICMP) is required before you can specify port numbers, or confusing extended ACLs with named ACLs that still follow the same match logic. To remember the fields, use the mnemonic “SPaP”: Source, Protocol, and Port, with Destination always included as the second field in the ACL statement.
300-410 IPv4 Access Control Lists Practice Question
This 300-410 practice question tests your understanding of ipv4 access control lists. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
When using an extended ACL to filter traffic, which fields can be matched? (Choose the most complete answer.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Source and destination IP addresses, protocol, and port numbers.
Extended ACLs (access control lists) operate at Layer 3 and Layer 4 of the OSI model, allowing matching on source and destination IP addresses, protocol (e.g., TCP, UDP, ICMP), and port numbers. This granularity enables precise traffic filtering beyond the source-only limitation of standard ACLs. Option B correctly lists all these matchable fields, making it the most complete answer.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Only source IP address.
Why it's wrong here
Incorrect. That is the capability of a standard ACL.
✓
Source and destination IP addresses, protocol, and port numbers.
Why this is correct
Correct. Extended ACLs can match these fields for fine-grained filtering.
Related concept
Read the scenario before looking for a memorised answer.
✗
Source IP address and destination port number only.
Why it's wrong here
Incorrect. Extended ACLs can match more fields, including protocol and source port.
✗
MAC address and IP address.
Why it's wrong here
Incorrect. MAC addresses are not matched by IP ACLs; they are used in MAC ACLs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between standard and extended ACLs, trapping candidates who forget that extended ACLs can match protocol and port numbers in addition to source and destination IP addresses, leading them to choose an incomplete option like C or A.
Detailed technical explanation
How to think about this question
Extended ACLs use access-list numbers 100-199 or 2000-2699 in Cisco IOS, and they evaluate the protocol field in the IP header (e.g., 6 for TCP, 17 for UDP) before checking port numbers. A common real-world scenario is blocking specific application traffic (e.g., HTTP on TCP port 80) between subnets while allowing other services, which requires matching both source/destination IPs and the destination port. Under the hood, the ACL processes entries sequentially until a match is found, and an implicit deny any any terminates the list.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 300-410 question in full detail.
IPv4 Access Control Lists — This question tests IPv4 Access Control Lists — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Source and destination IP addresses, protocol, and port numbers. — Extended ACLs (access control lists) operate at Layer 3 and Layer 4 of the OSI model, allowing matching on source and destination IP addresses, protocol (e.g., TCP, UDP, ICMP), and port numbers. This granularity enables precise traffic filtering beyond the source-only limitation of standard ACLs. Option B correctly lists all these matchable fields, making it the most complete answer.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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