IBM BladeCenter - Listening State

The following illustration shows the actions that occur when a port is in the blocking
state.
CPU
Port 2
Port 2
Port 1Port 1
Forwarding
Database
Forwarding
Database
BPDUs
BPDUs
Addresses
Discard
Forwarding
Blocking
Data
Packets
Data
Packets
Data
Packets
Data
Packets
Network
Management
Packets
Network
Management
Packets
Network SegmentNetwork Segment
Network SegmentNetwork Segment
Switching
Fabric
Switching
Fabric
Listening state
The listening state is the first change for a port from the blocking state. Listening is
an opportunity for the switch to receive BPDUs that might tell the switch that the
port should not continue to change 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:
v Discards frames received from the network segment to which it is attached
v Discards packets sent from another port on the switch for forwarding
v Does not add addresses to its forwarding database
v Receives BPDUs and directs them to the CPU
v Processes BPDUs received from the CPU
v Receives and responds to network management messages
128 IBM BladeCenter 4-Port Gb Ethernet Switch Module: Installation and User’s Guide