Blocking State; Learning State; Forwarding State - Cisco Nexus 7000 Series Configuration Manual

Configuring Rapid PVST+ Using Cisco NX-OS
2 The Layer 2 LAN port waits for the forward delay timer to expire, moves the Layer 2 LAN port to the
learning state, and restarts the forward delay timer.
3 In the learning state, the Layer 2 LAN port continues to block frame forwarding as it learns the end station
location information for the forwarding database.
4 The Layer 2 LAN port waits for the forward delay timer to expire and then moves the Layer 2 LAN port
to the forwarding state, where both learning and frame forwarding are enabled.

Blocking State

A Layer 2 LAN port in the blocking state does not participate in frame forwarding.
A Layer 2 LAN port in the blocking state performs as follows:
• Discards frames received from the attached segment.
• Discards frames switched from another port for forwarding.
• Does not incorporate the end station location into its address database. (There is no learning on a blocking
Layer 2 LAN port, so there is no address database update.)
• Receives BPDUs and directs them to the system module.
• Receives, processes, and transmits BPDUs received from the system module.
• Receives and responds to control plane messages.

Learning State

A Layer 2 LAN port in the learning state prepares to participate in frame forwarding by learning the MAC
addresses for the frames. The Layer 2 LAN port enters the learning state from the blocking state.
A Layer 2 LAN port in the learning state performs as follows:
• Discards frames received from the attached segment.
• Discards frames switched from another port for forwarding.
• Incorporates the end station location into its address database.
• Receives BPDUs and directs them to the system module.
• Receives, processes, and transmits BPDUs received from the system module.
• Receives and responds to control plane messages.

Forwarding State

A Layer 2 LAN port in the forwarding state forwards frames. The Layer 2 LAN port enters the forwarding
state from the learning state.
A Layer 2 LAN port in the forwarding state performs as follows:
• Forwards frames received from the attached segment.
• Forwards frames switched from another port for forwarding.
• Incorporates the end station location information into its address database.
Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x
Rapid PVST+
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