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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
322 Understanding and Troubleshooting the Spanning Tree Protocol
Listening State
The listening state is the first transition for a port from the
blocking state. Listening is an opportunity for the switch to
receive BPDUs that may tell the switch that the port should
not continue to transition to the forwarding state, but should
return to the blocking state (that is, a different port is a better
choice).
There is no address learning or packet forwarding from a port
in the listening state.
A port in the listening state does the following:
• Discards frames received from the network segment to
which it is attached.
• Discards packets sent from another port on the switch
for forwarding.
• Does not add addresses to its forwarding database
• Receives BPDUs and directs them to the CPU.
• Processes BPDUs received from the CPU.
• Receives and responds to network management
messages.