STP Fast Convergence Features Notes
STP Fast Convergence Features
1. Portfast
– Bypasses the listening and learning states on edge ports
– Used for end devices
– Global configuration
-> Applied to all non-trunking ports
SW1(config)# spanning-tree portfast default
– Interface configuration
SW1(config)# int fa0/1
spanning-tree portfast
– On trunk port
-> Should be used on trunk ports connected to
-> Routers
-> Servers
SW1(config)# int fa0/1
spanning-tree portfast trunk
2. Uplinkfast
– Bypasses listening and learning states
-> Enables blocked port immediately
– Used for direct link failurees
– Sends dummy packets for all connected end devices
-> Destined for STP multicast address
– Max-update-rate
-> Default is 150 packets per second
– Global configuration
SW1(config)# spanning-tree uplinkfast [max-update-rate <pps>]
3. Backbonefast
– To avoid max-age-timer incase of indirect link failure
– Sends Root Link Query (RLQ) out blocking port
-> Sent as soon as an inferior BPDU is received
– When RLQ acknowledgement is received, listening / learning procedure starts
– Global configuration
SW1(config)# spanning-tree backbonefast
show spanning-tree sum
– Will list all of the STP features that are enabled
show spanning-tree int <int> detail
– Detailed information
– Lists the number of BPDUs that are sent and received
