17-13
Catalyst 2960 Switch SoftwareConfiguration Guide
78-16881-01
Chapter17 Configuring Optiona l Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Enabling UplinkFast for Use with Redundant Links
UplinkFast cannot be enabled on VLANs that have been configured w ith a 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 the no spanning-tree vlan vlan-id priority global configuration command.
Note When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on
an individual VLAN.
You can configure the UplinkFast feature for rapid PVST+ or for the MSTP, but the feature remains
disabled (inactive) until you change the spanning-tree mode to PVST+.
Beginning in privileged EXEC mode, follow these steps to enable UplinkFast. This procedure is
optional.
When UplinkFast is enabled, the switch priority of all VLANs is set to 49152. If you change the path
cost to a value less than 3000 and you enable UplinkFast or UplinkFast is already enabled, the path cost
of all interfaces and VLAN trunks is increased by 3000 (if you change the path cost to 3000 or above,
the path cost is not altered). The changes to the switch priority and the path cost reduce the chance that
a switch will become the root switch.
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.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 spanning-tree uplinkfast [max-update-rate
pkts-per-second]
Enable UplinkFast.
(Optional) For pkts-per-second, the range is 0 to 32000 packets per
second; the default is 150.
If you set the rate to 0, station-learning frames are not g enerated,
and the spanning-tree topology converges more slowly after a loss
of connectivity.
Step3 end Return to privileged EXEC mode.
Step4 show spanning-tree summary Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.