easyMultiple Choice
200-201 Practice Question: An analyst is examining a syslog message from a…
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?
⚠ Common exam trap
Many candidates 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.
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
✓
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
HTTP traffic
Why it's wrong here
Port 123 is the syslog message's source and destination, identifying NTP, not HTTP (port 80/443). HTTP is tempting because analysts habitually associate denied traffic with web browsing, and blocking outbound HTTP would be the correct finding if the log showed tcp/80 or tcp/443.
- ✗
SNMP traffic
Why it's wrong here
Port 123 denotes NTP, whereas SNMP uses udp/161 and udp/162. SNMP is tempting because it is also UDP-based management traffic that firewalls commonly deny, and this log would indicate SNMP if the ports read 161 or 162 rather than 123.
- ✓
NTP traffic
Why this is correct
Both source and destination ports are 123, the well-known port for Network Time Protocol. The ASA deny message therefore identifies NTP traffic, not DNS, SNMP or syslog, which use ports 53, 161 and 514 respectively.
- ✗
DNS traffic
Why it's wrong here
DNS uses UDP port 53.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.