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Routing & Switching · Intermediate

Class Selector (CS)

DSCP values CS0-CS7 (multiples of 8) that preserve backward compatibility with 3-bit IP Precedence.

Definition

CS values set only the three high-order DSCP bits, so CS3 (24) maps to IP Precedence 3. CS6 is used for network control such as routing protocols, CS3 for call signaling and CS1 for scavenger traffic.

Example

Routing protocol packets are marked CS6 (48).

Exam tip

CSx decimal value = x times 8.

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