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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 10 Configuring STP
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 you enabled UplinkFast, making it unlikely that the switch will become
the root switch. The max-update-rate represents the number of multicast packets sent 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.
Note
When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast
on an individual VLAN.
Beginning in privileged EXEC mode, follow these steps to enable UplinkFast:
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.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree uplinkfast [max-update-rate
pkts-per-second]
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.
Step 3
end
Return to privileged EXEC mode.
Step 4
show spanning-tree
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
