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.
A network engineer runs the following command to troubleshoot an IPv4 Access Control Lists issue:
R1# debug ip packet 150 IP packet debugging is on for access list 150 *Mar 1 00:25:45.678: IP: s=192.168.1.1 (GigabitEthernet0/0), d=10.1.1.1, len 100, proto UDP, flags 0x0, sport 12345, dport 53, access list 150: matched line 10 permit udp host 192.168.1.1 host 10.1.1.1 eq 53 *Mar 1 00:25:45.679: IP: s=192.168.1.1 (GigabitEthernet0/0), d=10.1.1.1, len 100, proto TCP, flags 0x2, sport 12346, dport 53, access list 150: matched line 20 permit tcp host 192.168.1.1 host 10.1.1.1 eq 53
What does this output indicate?
DNS traffic from 192.168.1.1 to 10.1.1.1 is being permitted by ACL 150.
Both UDP and TCP DNS packets match permit lines.
DNS traffic from 192.168.1.1 to 10.1.1.1 is being denied by ACL 150.
Why wrong: The matches are on permit lines.
ACL 150 is applied outbound on GigabitEthernet0/0.
Why wrong: Direction is not shown.
ACL 150 has no line 10 or 20.
Why wrong: The debug shows those lines.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DNS traffic from 192.168.1.1 to 10.1.1.1 is being permitted by ACL 150.
The debug output shows that packets from source 192.168.1.1 to destination 10.1.1.1 with destination port 53 (DNS) are matching permit statements in ACL 150 (line 10 for UDP and line 20 for TCP). Since the ACL is permitting these packets, DNS traffic is allowed through the interface where the ACL is applied.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
DNS traffic from 192.168.1.1 to 10.1.1.1 is being permitted by ACL 150.
DNS traffic from 192.168.1.1 to 10.1.1.1 is being denied by ACL 150.
Why it's wrong here
The matches are on permit lines.
ACL 150 is applied outbound on GigabitEthernet0/0.
Why it's wrong here
Direction is not shown.
ACL 150 has no line 10 or 20.
Why it's wrong here
The debug shows those lines.
Common exam traps
Cisco often tests the misconception that 'debug ip packet' output shows only denied packets, but it actually shows all packets that match the ACL, whether permitted or denied, and the 'permit' or 'deny' keyword in the matched line is what determines the action.
Trap categories for this question
Command / output trap
Direction is not shown.
Detailed technical explanation
The 'debug ip packet' command with an ACL number filters debugging to only packets matching that ACL. The output shows both UDP and TCP packets to port 53, which is the well-known port for DNS. In real-world scenarios, DNS uses UDP by default but falls back to TCP for large responses or zone transfers; ACLs must permit both protocols to ensure full DNS functionality. The 'flags 0x2' in the TCP packet indicates a SYN packet, which is the first step of a TCP three-way handshake.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
IPv4 Access Control Lists — study guide chapter
Learn the concepts, then practise the questions
IPv4 Access Control Lists practice questions
Targeted practice on this topic area only
All 300-410 questions
2,152 questions across all exam domains
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 300-410 questions linked to Layer 3 Technologies.
Practise 300-410 questions linked to EIGRP Troubleshooting.
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
Practise 300-410 questions linked to BGP Troubleshooting.
Practise 300-410 questions linked to Route Redistribution.
Practise 300-410 questions linked to Policy-Based Routing (PBR).
Practise 300-410 questions linked to VRF-Lite.
Practise 300-410 questions linked to Route Maps and Route Filtering.
Practise 300-410 questions linked to Administrative Distance.
Practise 300-410 questions linked to Route Summarization.
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
IPv4 Access Control Lists — This question tests IPv4 Access Control Lists — Read the scenario before looking for a memorised answer..
The correct answer is: DNS traffic from 192.168.1.1 to 10.1.1.1 is being permitted by ACL 150. — The debug output shows that packets from source 192.168.1.1 to destination 10.1.1.1 with destination port 53 (DNS) are matching permit statements in ACL 150 (line 10 for UDP and line 20 for TCP). Since the ACL is permitting these packets, DNS traffic is allowed through the interface where the ACL is applied.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.