8 - Optional spanning-tree features

LEGACY CONVERGENGE OPTIMIZATIONS

- PortFast (also known as edge port)
  - Shouldn't be subject to forward delay
  - Affects TCN (topology change notificactions) generation
  -To enable portfast it has to be done at interface level
      spanning-tree portfast
  -To verify if an interface is portfast
      show spanning-tree int (interface) portfast
  -To enable portfast in all ports (global config) except the ones the switch receive bpdus (good practice)
      spanning-tree portfast default

- UplinkFast
  - Direct root port failure should reconverge inmediately if alternate port available
  - To enable uplink fast (global config)
       spanning-tree uplinkfast
  - One of the side effect of using uplink is the cost increment in the ports of the switch. So that will affect
    the path selecction in other switches

- Backbonefast
  - Indirect failures should start recalculating inmediately


STP FILTERS

- BPDU Filter
  - Filter bpdus in and out
- BPDU Guard
  - If BPDU is received shut port down
- Root Guard
  - Prevent the port advertising a superior BPDU to transition from designated (downstream) to root (upstream) port
  - If superior BPDU is received (better cost to the root bridge) shut port down
  - The difference with bpdu guard is that it shut port down only if receive superiot BPDU
- Filters can be configured globally in conjunction with PortFast


NOTES

- PortFast don't partipate in the spanning tree process so when the link flaps (shutdown), they will not generate
  topology change notificactions (TCN) which flush the cam table in all the switches and flood the network with traffic