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## 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#

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