ICMP

ICMP is used for network diagnostics and error messages (e.g., ping).

Updated: 2026-03-05

Definition

ICMP supports diagnostic tools (ping, traceroute) and communicates errors like unreachable networks.

It is important for troubleshooting and path discovery.

Key points

Used by ping and path diagnostics
Carries error/control messages
Can be filtered but should be controlled carefully

Common mistakes

Blocking all ICMP and breaking troubleshooting/PMTUD.
Assuming ICMP is always malicious.

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Related terms

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