Listening State - Cisco 7609 Configuration Manual

Chapter 15 Configuring STP and IEEE 802.1s MST

Listening State

The listening state is the first transitional state a Layer 2 LAN port enters after the blocking state. The
Layer 2 LAN port enters this state when STP determines that the Layer 2 LAN port should participate
in frame forwarding.
Figure 15-4 Interface 2 in Listening State
A Layer 2 LAN port in the listening state performs as follows:
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Figure 15-4
All segment
frames
Port 1
Station
addresses
BPDUs
Filtering System
database module
BPDUs
Data
frames
Port 2
Listening
BPDU and network
management frames
Discards frames received from the attached segment.
Discards frames switched from another LAN port for forwarding.
Does not incorporate end station location into its address database. (There is no learning at this
point, so there is no address database update.)
Receives BPDUs and directs them to the system module.
Receives, processes, and transmits BPDUs received from the system module.
Receives and responds to network management messages.
shows a Layer 2 LAN port in the listening state.
Forwarding
Network
management
and data frames
Frame
forwarding
Network
management
frames
All segment
frames
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
Understanding How STP Works
15-9