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Routing & Switching · Foundational

STP Port States

802.1D states: blocking, listening, learning, forwarding and disabled; RSTP collapses these to discarding, learning and forwarding.

Definition

Blocking receives BPDUs only (max age 20 s), listening processes BPDUs (forward delay 15 s), learning builds the MAC table (15 s), and forwarding sends data. RSTP merges disabled, blocking and listening into discarding.

Example

A port goes from blocking to forwarding in 50 seconds in 802.1D after an indirect failure.

Exam tip

Only learning and forwarding states learn MAC addresses.

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