7-8
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
—
Release 8.1
78-15486-01
Chapter 7 Configuring Spanning Tree
Understanding How STPs Work
Figure 7-4
Port 2 in Listening State
A port in the listening state performs as follows:
•
Discards frames received from the attached segment
•
Discards frames switched from another port for forwarding
•
Does not incorporate 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
•
Processes BPDUs received from the system module
•
Receives and responds to network management messages
Learning State
A port in the learning state prepares to participate in frame forwarding. The port enters the learning state
from the listening state.
Figure 7-5
shows a port in the learning state.
Filtering
database
Frame
forwarding
System
module
Port 1
BPDUs
All segment
frames
BPDU and network
management frames
All segment
frames
Forwarding
Listening
Station
addresses
Network
management
and data frames
Port 2
S5693
Network
management
frames
Data
frames
BPDUs
