An interface in the blocking state performs these functions: • Discards frames received on the interface • Discards frames that are switched from another interface for forwarding • Does not learn addresses • 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 decides that the interface should participate in frame forwarding. An interface in the listening state performs these functions:
• Discards frames received on the interface • Discards frames that are 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 these functions: • Discards frames received on the interface • Discards frames that are 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 these functions: • Receives and forwards frames that are received on the interface. • Forwards frames that are switched from another interface • 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. Configuring Spanning Tree Protocol Listening State Configuring Spanning Tree Protocol 6