Enabling Portfast - Cisco 6500 Series Software Configuration Manual

Enabling PortFast

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Enabling PortFast
Use PortFast only when connecting a single end station to a Layer 2 access port. Otherwise, you might
Caution
create a network loop.
To enable PortFast on a Layer 2 access port, perform this task:
Command
Step 1
Router(config)# interface {type
{port-channel port_channel_number}
Step 2
Router(config-if)# spanning-tree portfast
Step 3
Router(config-if)# spanning-tree portfast default
Step 4
Router(config-if)# end
Step 5
Router# show running interface {type
{port-channel port_channel_number}
1. type = ethernet, fastethernet, gigabitethernet, or tengigabitethernet
This example shows how to enable PortFast on Fast Ethernet interface 5/8:
Router# configure terminal
Router(config)# interface fastethernet 5/8
Router(config-if)# spanning-tree portfast
Router(config-if)# end
Router#
This example shows how to verify the configuration:
Router# 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
Router#
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
16-8
If a channel is blocked by loop guard and the channel breaks, spanning tree loses all the state
–
information. The individual physical ports may obtain the forwarding state with the designated
role, even if one or more of the links that formed the channel are unidirectional.
Note You can enable UniDirectional Link Detection (UDLD) to help isolate the link failure.
A loop may occur until UDLD detects the failure, but loop guard will not be able to
detect it.
Loop guard has no effect on a disabled spanning tree instance or a VLAN.
1
slot/port} |
1
slot/port} |
Chapter 16
Purpose
Selects an interface to configure.
Enables PortFast on a Layer 2 access port connected to a
single workstation or server.
Enables PortFast.
Exits configuration mode.
Verifies the configuration.
Configuring Optional STP Features
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