•  Hello Timer
  •  Forward delay Timer
  •  Max-age Timer

 

  • Hello Timer: How often switches send BPDU’s by default every 2 seconds
  • Forward delay Timer: how much long a port must spend time in both learning and listening state. By default 15 seconds
  • Max-age Timer: How long a switch will retain BPDU information from a neighbor switch before discarding it. By default 20 seconds

 

Improving STP Convergence

In many environments, a 30 second outage for every topology change is unacceptable. Cisco developed three proprietary features that improve STP convergence time:

  • PortFast
  • UplinkFast
  • BackboneFast