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ES-3124PWR Ethernet Switch
10-2 Spanning Tree Protocol
Once a stable network topology has been established, all bridges listen for Hello BPDUs (Bridge Protocol Data
Units) transmitted from the root bridge. If a bridge does not get a Hello BPDU after a predefined interval (Max
Age), the bridge assumes that the link to the root bridge is down. This bridge then initiates negotiations with other
bridges to reconfigure the network to re-establish a valid network topology.
10.1.3 STP Port States
STP assigns five port states (see next table) to eliminate packet looping. A bridge port is not allowed to go directly
from blocking state to forwarding state so as to eliminate transient loops.
Table 10-2 STP Port States
PORT STATE DESCRIPTION
Disabled STP is disabled (default).
Blocking Only configuration and management BPDUs are received and processed.
Listening All BPDUs are received and processed.
Learning All BPDUs are received and processed. Information frames are submitted to the learning
process but not forwarded.
Forwarding All BPDUs are received and processed. All information frames are received and forwarded.
10.2 STP Status
Click Advanced Application and then Spanning Tree Protocol in the navigation panel to display the STP status
as shown in the screen next.