Filter
Top Products
D
Spanning Tree Protocol
Introduction
When Spanning Tree Protocol determines a port should be transitioned to the forwarding
state, the following occurs:
•
•
•
•
•
•
The port is put into the listening state where it receives Bridge Protocol Data Units
(BPDUs) and passes them to the GbE Interconnect Switch’s CPU.
If no BPDUs that suggest the port should go to the blocking state are received, the BPDU
packets from the CPU are processed
— The port waits for the expiration of the forward delay timer. The port then moves to
the learning state.
— In the learning state, the port learns station location information from the source
address of packets and adds this information to its forwarding database.
— The expiration of the forwarding delay timer moves the port to the forwarding state,
where both learning and forwarding are enabled. At this point, the port forwards
packets.
Blocking State
A port in the blocking state does not forward packets. When the switch is booted, a BPDU is
sent to each port in the switch putting these ports into the blocking state. A switch initially
assumes it is the root, and then begins the exchange of BPDUs with other switches. This will
determine which switch in the network is the best choice for the root switch. If there is only
one switch on the network, no BPDU exchange occurs, the forward delay timer expires, and
the ports move to the listening state. All STP enabled ports enter the blocking state following
switch boot.
A port in the blocking state does the following:
Discards packets 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.
HP ProLiant BL e-Class C-GbE Interconnect Switch User Guide D-1
HP CONFIDENTIAL Codename: DeLorean Part Number: 263682-002 Last Saved On: 2/5/03 10:46 AM