Configuring Uplinkfast For Use With Redundant Links - Cisco Catalyst 2950 Software Manual

Configuring Advanced STP Features

Configuring UplinkFast for Use with Redundant Links

UplinkFast increases the switch priority to 49152 and adds 3000 to the STP path cost only if the port
used the default path cost before UplinkFast was enabled, making it unlikely that the switch will become
the root switch. The max-update-rate represents the number of multicast packets transmitted per second
(the default is 150 packets per second). UplinkFast cannot be enabled on VLANs that have been
configured for switch priority. To enable UplinkFast on a VLAN with switch priority configured, first
restore the switch priority on the VLAN to the default value by using a no spanning-tree vlan vlan-id
priority global configuration command.
When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on
Note
an individual VLAN.
Beginning in privileged EXEC mode, follow these steps to enable UplinkFast:
Command
Step 1
configure terminal
Step 2
spanning-tree uplinkfast [max-update-rate
pkts-per-second]
Step 3
end
Step 4
show spanning-tree
Step 5 copy running-config startup-config
When UplinkFast is enabled, the switch priority of all VLANs is set to 49152, and the path cost of all
interfaces and VLAN trunks is increased by 3000 if you did not modify the path cost from its default
setting. This change reduces the chance that the switch will become the root port. When UplinkFast is
disabled, the switch priorities of all VLANs and path costs of all interfaces are set to default values if
you did not modify them from their defaults.
To return the update packet rate to the default setting, use the no spanning-tree uplinkfast
max-update-rate global configuration command. To disable UplinkFast, use the no spanning-tree
uplinkfast command.
Catalyst 2950 Desktop Switch Software Configuration Guide
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Purpose
Enter global configuration mode.
Enable UplinkFast on the switch.
For pkts-per-second, the range is 0 to 65535 packets per second; the
default is 150.
If you set the rate to 0, station-learning frames are not generated,
and the STP topology converges more slowly after a loss of
connectivity.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Chapter 9 Configuring STP
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