Regarding a next change we have to do, we are studying spanning tree behaviour.

Does the following statement is true ?

In the case of topology change, if a new BPDU is received:

Currently: Root port A and designated ports B and C are forwarding, and ND port D are blocking.

If, after the new BPDU received: 1) the root port A become a designated port, and the designated port B become root port, do these two ports will simply stay in forwarding mode, or do these ports will restart the process with Listening state, Learning and Forwarding ?

2) the ND port D become designated port, so this port will immediately pass into Listening, Learning, and Forwarding state ?

1 Answer 1


Note that the original STP has been superseded by RSTP in 2002 as detailed in IEEE 802.1D. What you're asking is included in Clauses 17.28 and 17.29:

A change in port roles doesn't change the port state unless necessary- a designated port becoming root port, or a root port becoming designated should retain the forwarding state.

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