Cisco 3750G - Catalyst Integrated Wireless LAN Controller, Руководство по настройке

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20-16
Catalyst 3750 Switch Software Configuration Guide
OL-8550-02
Chapter 20 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
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.
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.
Note
If you use BackboneFast, you must enable it on all switches in the network. BackboneFast is not
supported on Token Ring VLANs. This feature is supported for use with third-party switches.
You can configure the BackboneFast 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 BackboneFast. This procedure is
optional.
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.
Command Purpose
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree backbonefast Enable BackboneFast.
Step 3 end Return to privileged EXEC mode.