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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

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