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.
A security analyst is investigating an alert that indicates a host is sending a large number of DNS queries to an external domain. The analyst wants to determine if the traffic is malicious and if it is using a DNS tunnel. Which type of analysis should the analyst perform to confirm the presence of a DNS tunnel?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Analyze the payload size and query frequency of the DNS packets to detect anomalous patterns.
Option A is correct because DNS tunneling typically involves encoding data within DNS queries or responses, resulting in abnormally large payload sizes and unusual query frequencies. By analyzing these specific packet attributes, an analyst can detect the anomalous patterns characteristic of a DNS tunnel, such as high query rates to a single domain or payloads exceeding standard DNS message sizes (e.g., >512 bytes for UDP). This direct inspection of DNS packet content is the most reliable method to confirm tunneling activity.
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.
✓
Analyze the payload size and query frequency of the DNS packets to detect anomalous patterns.
Why this is correct
DNS tunneling typically uses large payloads and unusual query patterns.
Related concept
Read the scenario before looking for a memorised answer.
✗
Check the volume of DNS traffic from the host to identify any increase over baseline.
Why it's wrong here
Increased volume alone is not definitive; it could be legitimate.
✗
Examine the source IP addresses of the DNS queries to see if they originate from multiple hosts.
Why it's wrong here
Source IP addresses can be spoofed or changed.
✗
Review the firewall logs to identify any blocked DNS queries to the external domain.
Why it's wrong here
Firewall logs may not show the payload details needed to confirm tunneling.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between detecting a general anomaly (e.g., high traffic volume) and confirming a specific technique (e.g., DNS tunneling), where candidates mistakenly choose a broad indicator like traffic volume (Option B) instead of the packet-level analysis that directly reveals the tunneling mechanism.
Trap categories for this question
Command / output trap
Firewall logs may not show the payload details needed to confirm tunneling.
Detailed technical explanation
How to think about this question
DNS tunneling exploits the DNS protocol to exfiltrate data by encoding it in subdomain labels or TXT records, often using base64 or similar encoding, which increases payload size beyond typical queries (e.g., a normal A-record query is ~40-60 bytes, while tunneled queries can exceed 200 bytes). Tools like `dnscat2` or `iodine` rely on high-frequency queries (e.g., hundreds per second) to maintain a covert channel, making payload size and query frequency key indicators. In real-world scenarios, a sudden spike in NXDOMAIN responses or queries to a rarely visited domain with unusually long hostnames can also hint at tunneling.
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: Analyze the payload size and query frequency of the DNS packets to detect anomalous patterns. — Option A is correct because DNS tunneling typically involves encoding data within DNS queries or responses, resulting in abnormally large payload sizes and unusual query frequencies. By analyzing these specific packet attributes, an analyst can detect the anomalous patterns characteristic of a DNS tunnel, such as high query rates to a single domain or payloads exceeding standard DNS message sizes (e.g., >512 bytes for UDP). This direct inspection of DNS packet content is the most reliable method to confirm tunneling activity.
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.
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 →
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.
This 200-201 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 200-201 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.