This 200-201 practice question tests your understanding of security monitoring. 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.
Exhibit
Refer to the exhibit.
Mar 1 12:34:56.789: %ASA-4-106023: Deny udp src inside:10.1.1.10/12345 dst outside:203.0.113.5/53 by access-group "OUTSIDE_IN" [0x0, 0x0]
Based on the exhibit, which type of traffic is being denied?
Refer to the exhibit.
Mar 1 12:34:56.789: %ASA-4-106023: Deny udp src inside:10.1.1.10/12345 dst outside:203.0.113.5/53 by access-group "OUTSIDE_IN" [0x0, 0x0]
A
Traffic permitted by the access group.
Why wrong: The log says 'Deny', so it is blocked, not permitted.
B
TCP traffic to a DNS server.
Why wrong: The log indicates UDP, not TCP.
C
UDP traffic from an internal host to an external DNS server.
The log matches UDP from inside to outside port 53.
D
ICMP traffic from an external host.
Why wrong: The log shows UDP and source is inside, not ICMP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
UDP traffic from an internal host to an external DNS server.
The exhibit shows an access control list (ACL) entry that denies UDP traffic from any source to any destination with a destination port of 53, which is the standard port for DNS. Since the ACL is applied inbound on an interface facing the internal network, it specifically blocks UDP traffic originating from an internal host destined for an external DNS server. This matches option C exactly.
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.
✗
Traffic permitted by the access group.
Why it's wrong here
The log says 'Deny', so it is blocked, not permitted.
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between UDP and TCP for DNS traffic, leading candidates to assume that all DNS traffic uses UDP, when in fact DNS can use TCP for larger responses or zone transfers, and the ACL only blocks UDP.
Trap categories for this question
Command / output trap
The log shows UDP and source is inside, not ICMP.
Detailed technical explanation
How to think about this question
DNS primarily uses UDP on port 53 for standard queries, but it can fall back to TCP for zone transfers or when responses exceed 512 bytes (per RFC 1035). In a security context, blocking UDP/53 outbound can prevent internal hosts from performing DNS lookups to external servers, which is a common technique to enforce DNS filtering or prevent data exfiltration via DNS tunneling. The ACL entry 'deny udp any any eq 53' is protocol-specific and does not affect TCP-based DNS traffic.
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.
Security Monitoring — This question tests Security Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: UDP traffic from an internal host to an external DNS server. — The exhibit shows an access control list (ACL) entry that denies UDP traffic from any source to any destination with a destination port of 53, which is the standard port for DNS. Since the ACL is applied inbound on an interface facing the internal network, it specifically blocks UDP traffic originating from an internal host destined for an external DNS server. This matches option C exactly.
What should I do if I get this 200-201 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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