- A
The 'log' keyword causes the router to generate a syslog message for every packet that matches the ACE.
Why wrong: Incorrect. The router logs the first match immediately, then rate-limits subsequent matches, typically logging once every 5 minutes.
- B
The log message includes the source and destination IP addresses and the protocol.
Correct. The log entry typically shows the source IP, destination IP, protocol (e.g., TCP), and the interface where the match occurred.
- C
The 'log' keyword can be used with both permit and deny ACEs.
Correct. You can log matches for both permit and deny entries, though logging denies is more common for troubleshooting.
- D
The 'log' keyword is only available in extended ACLs, not standard ACLs.
Why wrong: Incorrect. The 'log' keyword is available in both standard and extended ACLs, though in standard ACLs it only logs the source IP.
- E
Using the 'log' keyword significantly improves router performance by offloading logging to the CPU.
Why wrong: Incorrect. Logging consumes CPU resources and can degrade performance if used excessively, especially on high-traffic interfaces.
Quick Answer
The answer is that the log keyword in IPv4 ACLs can be used with both permit and deny ACEs. This is correct because when the log keyword is appended to any ACL entry, the router generates a syslog message for every packet that matches that specific rule, capturing critical details such as source and destination IP addresses, the protocol (TCP, UDP, ICMP), and for TCP/UDP, the source and destination port numbers. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of ACL troubleshooting and security monitoring, often appearing in a multiple-choice question where a common trap is assuming logging only applies to deny statements. A useful memory tip is to remember that logging is a tool for visibility, not enforcement—it works on any match, whether you are permitting or denying traffic, so think "log both, block or allow."
300-410 IPv4 Access Control Lists Practice Question
This 300-410 practice question tests your understanding of ipv4 access control lists. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Which TWO statements about the 'log' keyword in IPv4 ACL entries are correct? (Choose TWO.)
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
The log message includes the source and destination IP addresses and the protocol.
Option B is correct because when the 'log' keyword is configured on an ACL entry, the router generates a syslog message that includes the source and destination IP addresses, the protocol (e.g., TCP, UDP, ICMP), and for TCP/UDP, the source and destination port numbers. This logging provides essential information for troubleshooting and security monitoring.
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.
- ✗
The 'log' keyword causes the router to generate a syslog message for every packet that matches the ACE.
Why it's wrong here
Incorrect. The router logs the first match immediately, then rate-limits subsequent matches, typically logging once every 5 minutes.
- ✓
The log message includes the source and destination IP addresses and the protocol.
Why this is correct
Correct. The log entry typically shows the source IP, destination IP, protocol (e.g., TCP), and the interface where the match occurred.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The 'log' keyword can be used with both permit and deny ACEs.
Why this is correct
Correct. You can log matches for both permit and deny entries, though logging denies is more common for troubleshooting.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The 'log' keyword is only available in extended ACLs, not standard ACLs.
Why it's wrong here
Incorrect. The 'log' keyword is available in both standard and extended ACLs, though in standard ACLs it only logs the source IP.
- ✗
Using the 'log' keyword significantly improves router performance by offloading logging to the CPU.
Why it's wrong here
Incorrect. Logging consumes CPU resources and can degrade performance if used excessively, especially on high-traffic interfaces.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that the 'log' keyword logs every packet, when in fact it uses rate-limiting to avoid overwhelming the router's CPU.
Trap categories for this question
Keyword trap
Incorrect. The 'log' keyword is available in both standard and extended ACLs, though in standard ACLs it only logs the source IP.
Detailed technical explanation
How to think about this question
Under the hood, Cisco IOS uses a rate-limited logging mechanism for ACL entries: the first matching packet triggers a syslog message, and subsequent matches are suppressed for a default interval (e.g., 5 seconds) to prevent CPU overload. In real-world scenarios, this behavior is critical for high-traffic interfaces where logging every packet would cause severe performance degradation or even router crashes. The 'log-input' keyword extends this by including the ingress interface and source MAC address in the log message.
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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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IPv4 Access Control Lists — study guide chapter
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FAQ
Questions learners often ask
What does this 300-410 question test?
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: The log message includes the source and destination IP addresses and the protocol. — Option B is correct because when the 'log' keyword is configured on an ACL entry, the router generates a syslog message that includes the source and destination IP addresses, the protocol (e.g., TCP, UDP, ICMP), and for TCP/UDP, the source and destination port numbers. This logging provides essential information for troubleshooting and security monitoring.
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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Last reviewed: Jun 24, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
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