Spanning-Tree Uplinkfast - Cisco Catalyst 3750 Command Reference Manual
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spanning-tree uplinkfast
spanning-tree uplinkfast
Use the spanning-tree uplinkfast global configuration command on the switch stack or on a standalone
switch to accelerate the choice of a new root port when a link or switch fails or when the spanning tree
reconfigures itself. Use the no form of this command to return to the default setting.
Syntax Description
max-update-rate pkts-per-second
Defaults
UplinkFast is disabled.
The update rate is 150 packets per second.
Command Modes
Global configuration
Command History
Release
12.1(11)AX
12.1(14)EA1
Usage Guidelines
Use this command only on access switches.
The UplinkFast feature is supported only when the switch is running per-VLAN spanning-tree plus
(PVST+). It is not supported when the switch is operating in the rapid-PVST+ or multiple spanning-tree
(MST) mode.
When you enable UplinkFast, it is enabled for the entire switch and cannot be enabled for individual
VLANs.
When you enable or disable UplinkFast, cross-stack UplinkFast (CSUF) also is automatically enabled
or disabled on all nonstack port interfaces. CSUF accelerates the choice of a new root port when a link
or switch fails or when spanning tree reconfigures itself.
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 reduces 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.
When spanning tree detects that the root port has failed, UplinkFast immediately changes to an alternate
root port, changing the new root port directly to forwarding state. During this time, a topology change
notification is sent.
Catalyst 3750 Switch Command Reference
2-456
spanning-tree uplinkfast [max-update-rate pkts-per-second]
no spanning-tree uplinkfast [max-update-rate]
Modification
This command was introduced.
The max-update-rate keyword was added.
Chapter 2 Catalyst 3750 Switch Cisco IOS Commands
(Optional) The number of packets per second at which update
packets are sent. The range is 0 to 32000.
78-16181-01
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