Mission 020

Engineer Briefing

A network engineer needs evidence.

When a user says:

"The network is not working."

The engineer does not immediately change configurations.

They ask:

• Can the device reach the gateway?
• Can it reach another computer?
• Where does communication fail?

One of the most important tools for answering these questions is:

ICMP

Mission Objectives

By the end of this mission, students should understand:

✅ What ICMP is.

✅ How ping works.

✅ ICMP request and reply messages.

✅ How routers use ICMP error messages.