Enabling Uplinkfast - Cisco Catalyst 4500 Series Configuration Manual

Enabling UplinkFast

Figure 23-3
Switch A
(Root)
Enabling UplinkFast
UplinkFast increases the bridge priority to 49,152 and adds 3000 to the spanning tree port cost of all
interfaces on the switch, making it unlikely that the switch becomes the root switch. The
max_update_rate value represents the number of multicast packets transmitted per second (the default
is 150 packets per second [pps]).
UplinkFast cannot be enabled on VLANs that have been configured for bridge priority. To enable
UplinkFast on a VLAN with bridge priority configured, restore the bridge priority on the VLAN to the
default value by entering a no spanning-tree vlan vlan_ID priority command in global configuration
mode.
When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on
Note
an individual VLAN.
To enable UplinkFast, perform this task:
Command
Step 1
Switch(config)# [no] spanning-tree uplinkfast
[max-update-rate max_update_rate]
Step 2
Switch(config)# end
Step 3
Switch# show spanning-tree vlan vlan_ID
This example shows how to enable UplinkFast with a maximum update rate of 400 pps:
Switch(config)# spanning-tree uplinkfast max-update-rate 400
Switch(config)# exit
Switch#
This example shows how to verify which VLANS have UplinkFast enabled:
Switch# show spanning-tree uplinkfast
UplinkFast is enabled
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
23-12
UplinkFast After Direct Link Failure
L1
L2
Link failure
Switch C
Switch B
L3
UplinkFast transitions port
directly to forwarding state
Purpose
Enables UplinkFast.
Use the no keyword to disable UplinkFast and restore the
default rate, use the command.
Exits configuration mode.
Verifies that UplinkFast is enabled on that VLAN.
Chapter 23 Configuring Optional STP Features
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