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D-Link DHS-3224V Switch User’s Guide
28
Transition States
Each port on a switch using STP exists is in one of the following five states:
Figure 5.4 below illustrates the STP port transition states.
Figure 5-4. STP Transition States
Port State Transition
When you enable STP, every port on every switch in
the network goes through the blocking state and then transitions through the states of listening and learning at
power up. If properly configured, each port stabilizes to the forwarding or blocking state.
No packets (except BPDUs) are forwarded from, or received by, STP enabled ports until the forwarding state is
enabled for that port.
A port transitions from one state to another as follows:
- From initialization (switch boot) to blocking
- From blocking to listening or to disabled
- From listening to learning or to disabled
- From learning to forwarding or to disabled
- From forwarding to disabled
- From disabled to blocking
Blocking
The port is blocked from forwarding or receiving
packets.
Listening
The port is waiting to receive BPDU packets that may
tell the port to go back to the blocking state.
Learning
The port is adding addresses to its forwarding database,
but not yet forwarding packets.
Forwarding
The port is forwarding packets.
Disabled
The port only responds to network managemen
t
messages and must return to the blocking state first.