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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
320 Understanding and Troubleshooting the Spanning Tree Protocol
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.
• Does not transmit BPDUs received from the CPU.
• Receives and responds to network management
messages.