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Networking Intermediate

What is ICMP (Internet Control Message Protocol)?

A network protocol used for diagnostic and error reporting, including ping and traceroute functionality.

ICMP sends error messages and operational information between network devices. Ping uses ICMP Echo Request/Reply to test reachability and measure round-trip time. Traceroute uses ICMP Time Exceeded messages to discover the network path.

Common ICMP messages include Destination Unreachable, Time Exceeded, Redirect, and Source Quench. While essential for network diagnostics, ICMP is often restricted by firewalls to prevent information disclosure and DDoS amplification attacks.

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