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Catalyst 2950 Desktop Switch Software Configuration Guide
78-11380-03
Chapter 9 Configuring STP
Understanding Basic STP Features
Listening State
The listening state is the first state an interface enters after the blocking state. The interface enters this
state when STP 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
An 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
An 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
An interface in the disabled state does not participate in frame forwarding or STP. 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
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