Spanning-Tree Uplinkfast - Cisco Catalyst 3560X-24P Command Reference Manual

Chapter 2 Catalyst 3750-X and 3560-X Cisco IOS Commands

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
12.2(53)SE2
Usage Guidelines
Use this command only on access switches.
You can configure the UplinkFast feature for rapid PVST+ or for multiple spanning-tree (MST) mode,
but the feature remains disabled (inactive) until you change the spanning-tree mode to PVST+.
When you enable UplinkFast, it is enabled for the entire switch and cannot be enabled for individual
VLANs.
On Catalyst 3750-X switches, 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.
OL-21522-02
spanning-tree uplinkfast [max-update-rate pkts-per-second]
no spanning-tree uplinkfast [max-update-rate]
Modification
This command was introduced.
(Optional) The number of packets per second at which update
packets are sent. The range is 0 to 32000.
Catalyst 3750-X and 3560-X Switch Command Reference
spanning-tree uplinkfast
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