Cisco Systems OL-29225-01 Listening State, Learning State, Forwarding State, Disabled State

8-7
Cisco IOS Software Configuration Guide for Cisco Aironet Access Points
OL-30644-01
Chapter8 Configuring Spanning Tree Protocol
Understanding Spanning Tree Protocol
•Discards frames received on the port
•Does not learn addresses
•Receives BPDUs
Note If a access point/bridge port is blocked, some broadcast or multicast packets can reach a forwarding port
on the access point/bridge and cause the bridging logic to switch the blocked port into listening state
momentarily before the packets are dropped at the blocked port.
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
•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
•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
•Learns addresses
•Receives BPDUs
Disabled State
An 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
•Does not learn addresses