5. ICMP

Question 1

What is the primary role of ICMP in network communication?

Answer 1

ICMP is used for error reporting and diagnostics, helping maintain and troubleshoot network functionality.

Question 2

What are ICMP Echo Request and Echo Reply messages used for?

Answer 2

They are used by the ping command to test connectivity and measure round trip time between devices.

Question 3

What is the purpose of an ICMP Destination Unreachable message?

Answer 3

To notify the sender that a packet could not reach its intended destination due to issues such as unavailable routes or unreachable hosts.

Question 4

How does the Time Exceeded message in ICMP help prevent packet looping?

Answer 4

It informs the sender that the packet’s TTL (Time-To-Live) has expired, indicating it has been discarded to avoid infinite looping.

Question 5

What is the significance of ICMP Redirect messages?

Answer 5

Redirect messages inform hosts of a better route to a destination, optimizing routing paths.

Question 6

Why might ICMP messages be blocked by a firewall?

Answer 6

To prevent potential misuse in network reconnaissance, such as ping sweeps or ICMP flooding in denial-of-service attacks.