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14-6
Software Configuration Guide—Release 12.2(25)SG
OL-7659-03
Chapter 14 Configuring STP Features
Enabling PortFast
Note Because the purpose of PortFast is to minimize the time that access ports must wait for spanning tree to
converge, it is most effective when used on access ports. If you enable PortFast on a port connecting to
another switch, you risk creating a spanning tree loop.
Enabling PortFast
Caution Use PortFast only when connecting a single end station to a Layer 2 access port. Otherwise, you might
create a network loop.
To enable PortFast on a Layer 2 access port to force it to enter the forwarding state immediately, perform
this task:
This example shows how to enable PortFast on Fast Ethernet interface 5/8:
Switch(config)# interface fastethernet 5/8
Switch(config-if)# spanning-tree portfast
Switch(config-if)# end
Switch#
This example shows how to verify the configuration:
Switch# show running-config interface fastethernet 5/8
Building configuration...
Current configuration:
!
interface FastEthernet5/8
no ip address
switchport
switchport access vlan 200
switchport mode access
spanning-tree portfast
end
Switch#
Command Purpose
Step 1
Switch(config)# interface {{fastethernet |
gigabitethernet | tengigabitethernet}
slot
/
port
}
| {port-channel
port_channel_number
}
Specifies an interface to configure.
Step 2
Switch(config-if)# [no] spanning-tree portfast
Enables PortFast on a Layer 2 access port connected to a
single workstation or server.
You can use the no keyword to disable PortFast.
Step 3
Switch(config-if)# end
Exits configuration mode.
Step 4
Switch# show running interface {{fastethernet |
gigabitethernet | tengigabitethernet}
slot
/
port
}
| {port-channel
port_channel_number
}
Verifies the configuration.