CPENT Network And Perimeter Exploitation Practice Question
A pentester needs to verify whether a remote server is listening on a specific UDP port, say port 123 (NTP). They send a UDP packet, but the target responds with an ICMP Port Unreachable message. What does this response indicate about the port?
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
✓
The port is closed.
An ICMP Port Unreachable message (Type 3, Code 3) indicates that the target UDP port is closed.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The host is offline.
Why it's wrong here
An ICMP unreachable message comes from the live operating system IP stack, proving the host is online.
- ✗
The port is filtered by a firewall.
Why it's wrong here
A firewall drop typically results in no response or an ICMP administratively prohibited message.
- ✗
The port is open and active.
Why it's wrong here
An open UDP port typically responds with valid service data or no ICMP error.
- ✓
The port is closed.
Why this is correct
ICMP Port Unreachable confirms the UDP port is closed.
About these practice questions
This CPENT question is part of Courseiva's 276-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official EC-Council exam blueprint
This CPENT practice question is part of Courseiva's free EC-Council 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 CPENT exam.