Configure the Spanning-Tree portfast Setting

Any port that is directly connected to an end station cannot create bridging loops. Therefore, the port can rapidly transition to the forwarding state by skipping the learning and listening states. To enable immediate transition into the forwarding state, you can enable the STP portfast feature. The portfast feature immediately transitions the port into STP forwarding mode upon link-up. The port still participates in STP, so if the port is to be a part of the loop, the port eventually transitions into STP blocking mode.

In switch A, run the following commands as port 20 is connected to a host.

1. Enter the configuration mode for the interface.

   NEM-1 SEFOS# configure terminal
   NEM-1 SEFOS(config)# interface extreme-ethernet 0/20
   NEM-1 SEFOS(config-if)#
   

   Valid interfaces include physical interfaces and port-channel logical interfaces (port-channel port_channel_number).

2. Shut down the interface.

   NEM-1 SEFOS(config-if)# shutdown
   NEM-1 SEFOS(config-if)#
   

3. Change the portfast setting.

   NEM-1 SEFOS(config-if)# spanning-tree portfast
    
   Warning: portfast should only be enabled on ports connected to a single host. Connecting hubs, concentrators, switches, bridges, etc... to this interface when portfast is enabled, can cause temporary bridging loops.
   Use with CAUTION
    
   NEM-1 SEFOS(config-if)# no shutdown
   NEM-1 SEFOS(config-if)# end
   NEM-1 SEFOS#
   

4. Review the portfast status.

   NEM-1 SEFOS# show spanning-tree interface extreme-ethernet 0/20 portfast
    
   spanning-tree portfast is Enabled
   NEM-1 SEFOS#
   

5. Reset the default spanning tree portfast value for the interface.

   NEM-1 SEFOS# configure terminal
   NEM-1 SEFOS(config)# interface extreme-ethernet 0/20
   NEM-1 SEFOS(config-if)# no spanning-tree portfast
    
   Warning:Portfast has been configured on this port but will have effect only when the interface is shutdown
    
   NEM-1 SEFOS(config-if)# end
   NEM-1 SEFOS#
   

6. Review the portfast status.

   NEM-1 SEFOS# show spanning-tree interface extreme-ethernet 0/20 portfast
    
   spanning-tree portfast is Disabled
    
   NEM-1 SEFOS#