STP Portfast Options

When configuring Spanning Tree Protocol (STP), the use of the STP Portfast feature is an important consideration. When using RSTP such a configuration is called creating STP - RSTP EdgePorts. When configuring such edgports, there are three options that are presented, as shown with this context sensitive help of the CLI:

Switch(config)#spanning-tree portfast ?
  edge       Spanning tree portfast edge options
  network    Spanning tree portfast network options
  normal     Spanning tree portfast normal options

Switch(config)#spanning-tree portfast edge ?
  bpdufilter Enable portfast edge bpdu filter on this switch
  bpduguard  Enable portfast edge bpdu guard on this switch
  default    Enable portfast edge by default on all access ports

Switch(config)#spanning-tree portfast network ?
  default    Enable portfast network by default on all ports

Switch(config)#spanning-tree portfast normal ?
  default    Enable normal behavior by default on all ports

• portfast edge is used to configure a port on which an end device is connected, such as a PC. All ports directly connected to end devices cannot create bridging loops in the network. Therefore, the edge port directly transitions to the forwarding state, and skips the listening and learning stages. However, the specific command configures a port such that if it receives a BPDU, it immediately loses its edge port status and becomes a normal spanning-tree port.

• You use the portfast network on trunk ports to enable bridge assurance feature which protects against loops by detecting unidirectional links in the STP topology. But normally bridge assurance is enabled by default.

• A spanning tree portfast normal port is one that functions in the default manner for spanning tree. Under normal circumstances it will transition from the Listening, Learning, Forwarding stages based on the default timers.

The above commands are global configuration commands and are applied to all ports on the switch. For port-specific configurations, these commands are applied in the interface configuration mode of the CLI.