Configuring UplinkFast
How to configure UplinkFast

UplinkFast is enabled on a switch rather than on a port. When enabled, it increases the bridge priority to 49,152 and adds a value of 3000 to the spanning tree port cost of all interfaces on the switch, which makes it unlikely that the switch will become the root switch. If bridge priority or port cost has been manually configured on a switch, UplinkFast will not alter those spanning tree values; it will only alter default values.

Enabling UplinkFast affects all VLANs on the switch. You cannot configure UplinkFast on an individual VLAN.

Configuring UplinkFast
To enable or disable UplinkFast, use this command:

Switch(config)#[no] spanning-tree uplinkfast [max-update-rate max_update_rate]

The max_update_rate value represents the number of dummy multicast packets transmitted per second when a failover occurs. The default value is 150 packets per second (pps).

For example this is the command that would be used to enable UplinkFast with a maximum update rate of 400 pps:

Switch(config)#spanning-tree uplinkfast max-update-rate 400
NOTE:

UplinkFast should only be configured on access switches.

Verifying UplinkFast
Use the show spanning-tree uplinkfast command to verify UplinkFast configuration. This example shows how to identify which VLANS have UplinkFast enabled.