Cisco Systems 3750E Enabling Cross-Stack UplinkFast, Enabling BackboneFast, Uplinkfast command

Chapter 20 Configuring Optional Spanning-Tree Features

Configuring Optional Spanning-Tree Features

Beginning in privileged EXEC mode, follow these steps to enable UplinkFast and CSUF. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	spanning-tree uplinkfast [max-update-rate	Enable UplinkFast.
	pkts-per-second]	(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 generated,
		and the spanning-tree topology converges more slowly after a loss
		of connectivity.
		When you enter this command, CSUF also is enabled on all
		nonstack port interfaces.
Step 3
	end	Return to privileged EXEC mode.
Step 4
	show spanning-tree summary	Verify your entries.
Step 5
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

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-rateglobal configuration command. To disable UplinkFast, use the no spanning-tree

uplinkfast command.

Enabling Cross-Stack UplinkFast

When you enable or disable the UplinkFast feature by using the spanning-tree uplinkfast global configuration command, CSUF is automatically globally enabled or disabled on nonstack port interfaces.

For more information, see the “Enabling UplinkFast for Use with Redundant Links” section on page 20-15.

To disable UplinkFast on the switch and all its VLANs, use the no spanning-tree uplinkfast global configuration command.

Enabling BackboneFast

You can enable BackboneFast to detect indirect link failures and to start the spanning-tree reconfiguration sooner.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
20-16	OL-9775-02