Enabling The Port Fast Feature - Cisco WS-C2950-24 Configuration Manual

Configuring STP

Enabling the Port Fast Feature

Caution
Command
Step 1 configure terminal
Step 2
interface interface
Step 3
spanning-tree portfast
Step 4
end
Step 5
show running-config
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
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The Port Fast feature brings a port directly from a blocking state into a forwarding
state. This feature is useful when a connected server or workstation times out
because its port is going through the normal cycle of STP status changes. A port
with Port Fast enabled only goes through the normal cycle of STP status changes
when the switch is restarted.
Enabling this feature on a port connected to a switch or hub could prevent STP
from detecting and disabling loops in your network, and this could cause
broadcast storms and address-learning problems.
You can modify the following Port Fast parameters:
Port Fast—Enable to bring the port more quickly to an STP forwarding state.
•
• Path Cost —A lower path cost represents higher-speed transmission. This can
affect which port remains enabled in the event of a loop.
Enter a number from 1 to 65535. The default is 100 for 10 Mbps, 19 for
100 Mbps, 14 for 155 Mbps (ATM), 4 for 1 Gbps, 2 for 10 Gbps, and 1 for
interfaces with speeds greater than 10 Gbps.
Priority —Number used to set the priority for a port. A higher number has
•
higher priority. Enter a number from 0 to 65535.
Enabling this feature on a port connected to a switch or hub could prevent STP
from detecting and disabling loops in your network. Beginning in privileged
EXEC mode, follow these steps to enable the Port Fast feature:
Purpose
Enter global configuration mode.
Enter interface configuration mode, and enter the port to be
configured.
Enable the Port Fast feature for the port.
Return to privileged EXEC mode.
Verify your entry.
Chapter 6 Configuring the System
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