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Networking Fundamentals · Foundational

Cyclic Redundancy Check (CRC)

An error-detecting code based on polynomial division, used in Ethernet's FCS and in storage systems.

Definition

CRC-32 can detect all single-bit errors, burst errors up to 32 bits and the vast majority of other corruption. It is computed in hardware by NICs and switch ports. CRC is stronger than simple checksums but provides no protection against deliberate tampering.

Example

A NIC computes CRC-32 over each outbound frame and places it in the FCS.

Exam tip

CRC is an integrity check against accidental errors, not a security hash.

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