Spanning Tree
Cisco PVST+ 802.1d Root Bridge Elect Root Bridge -> Lowest Bridge ID Bridge ID -> Priority + MAC All ports on the Root Bridge are Designated ports and are in a Forwarding State. Root Bridge is the Reference Point for everyone else. Each switch in the network looks for the best path to the root bridge. Decision is made based on the path cost. If the path cost is the same Port ID breaks tie. All other ports towards the Root Bridge are put in Blocking/Alternate state. Path Cost Ethernet = 100 Fast Ethernet = 19 Gigabit = 4 10 Gigabit = 2 Port States - Convergence takes 50 seconds Disabled Blocking - 20 seconds Listening - 15 seconds Learning - 15 seconds Forwarding Network Changes BPDUs - Hello timer is sent every 2 seconds TCNs are sent up stream to each device notifing the switch of a change in the topology. TCAs are sent back down stream to acknowledge the changes. This is done untill the TCN reaches the Root Bridge. Rapid PVST+ 802.1w Root Bridge Elected the same way as 802.1d P...