Interlogix NS3500-28T-4S, User Manual

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after a topology change.
Each port on a switch using STP exists is in one of the following five states:

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 management messages and must return to the blocking
state first
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
Figure 4-6-1
STP Port State Transitions