Implement Spanning Tree Protocol (STP)

Each configuration BPDU contains this information:

•The unique bridge ID of the switch that the sending switch identifies as the root switch

•The spanning-tree path cost to the root

•The bridge ID of the sending switch

•Message age

•The identifier of the sending interface

•Values for the hello, forward delay, and max-age protocol timers 

Each Layer 2 interface on a switch using spanning tree exists in one of these states:

•Blocking—The interface does not participate in frame forwarding.

•Listening—The first transitional state after the blocking state when the spanning tree decides that the interface should participate in frame forwarding.

•Learning—The interface prepares to participate in frame forwarding.

•Forwarding—The interface forwards frames.

•Disabled—The interface is not participating in spanning tree because of a shutdown port, no link on the port, or no spanning-tree instance running on the port.

An interface moves through these states:

•From initialization 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