Quick Answer
The answer is NTP traffic. This is correct because the firewall log entry shows a UDP denial on port 123, which is the well-known port assigned to the Network Time Protocol (NTP) for clock synchronization between devices. When identifying protocols from port numbers in firewall logs, you must map the destination port to its standard service—here, both source and destination use port 123, confirming NTP rather than other UDP-based services like DNS (port 53) or DHCP (ports 67/68). On the Cisco CyberOps Associate 200-201 exam, this type of question tests your ability to read syslog messages like %ASA-4-106023 and quickly correlate port numbers to protocols, a common task in security monitoring. A frequent trap is confusing NTP with SNMP (port 161) or Syslog (port 514), so always double-check the port number. Memory tip: Think of NTP as the “timekeeper” on port 123—just remember “1-2-3, sync your clock with me.”
This 200-201 practice question tests your understanding of network intrusion analysis. 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.
An analyst is examining a syslog message from a Cisco ASA showing: %ASA-4-106023: Deny udp src outside:192.0.2.1/123 dst inside:10.0.0.5/123. Which type of traffic is being denied?
HTTP traffic
Why wrong: HTTP uses TCP port 80.
SNMP traffic
Why wrong: SNMP uses UDP ports 161 and 162.
NTP traffic
NTP uses UDP port 123.
DNS traffic
Why wrong: DNS uses UDP port 53.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
NTP traffic
The syslog message %ASA-4-106023 shows a UDP deny from source 192.0.2.1 port 123 to destination 10.0.0.5 port 123. Port 123 is the well-known port for Network Time Protocol (NTP), which is used for clock synchronization. Therefore, the denied traffic is NTP traffic.
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.
HTTP traffic
SNMP traffic
NTP traffic
DNS traffic
Common exam traps
The trap here is that candidates may confuse port 123 with other common UDP services like DNS (port 53) or SNMP (ports 161/162), or assume the '123' is a random number rather than a standard port assignment.
Detailed technical explanation
NTP operates over UDP port 123 and uses a hierarchical system of stratum levels to synchronize clocks across networks. The Cisco ASA syslog message 106023 is generated when an access control list (ACL) denies a packet; the format includes the protocol, source/destination IPs, and ports, making it straightforward to identify the application by port number. In real-world scenarios, blocking NTP can cause time drift, affecting logging accuracy and authentication protocols like Kerberos.
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
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FAQ
Network Intrusion Analysis — This question tests Network Intrusion Analysis — Read the scenario before looking for a memorised answer..
The correct answer is: NTP traffic — The syslog message %ASA-4-106023 shows a UDP deny from source 192.0.2.1 port 123 to destination 10.0.0.5 port 123. Port 123 is the well-known port for Network Time Protocol (NTP), which is used for clock synchronization. Therefore, the denied traffic is NTP traffic.
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.
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Last reviewed: Jun 25, 2026
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.
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