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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 13 Configuring STP
Understanding Spanning-Tree Features
Receives BPDUs
Listening State
The listening state is the first state a Layer 2 interface enters after the blocking state. The interface enters
this state when the spanning tree determines that the interface should participate in frame forwarding.
An interface in the listening state performs as follows:
Discards frames received on the port
Discards frames switched from another interface for forwarding
Does not learn addresses
Receives BPDUs
Learning State
A Layer 2 interface in the learning state prepares to participate in frame forwarding. The interface enters
the learning state from the listening state.
An interface in the learning state performs as follows:
Discards frames received on the port
Discards frames switched from another interface for forwarding
Learns addresses
Receives BPDUs
Forwarding State
A Layer 2 interface in the forwarding state forwards frames. The interface enters the forwarding state
from the learning state.
An interface in the forwarding state performs as follows:
Receives and forwards frames received on the port
Forwards frames switched from another port
Learns addresses
Receives BPDUs
Disabled State
A Layer 2 interface in the disabled state does not participate in frame forwarding or in the spanning tree.
An interface in the disabled state is nonoperational.
A disabled interface performs as follows:
Discards frames received on the port
Discards frames switched from another interface for forwarding
Does not learn addresses
Does not receive BPDUs