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Cisco IE 3000 Switch Software Configuration Guide
OL-13018-03
Chapter 20 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Enabling UplinkFast for Use with Redundant Links
UplinkFast cannot be enabled on VLANs that have been configured with a switch priority. To enable
UplinkFast on a VLAN with switch priority configured, first restore the switch priority on the VLAN to
the default value by using the
no spanning-tree vlan
vlan-id
priority
global configuration command.
Note
When you enable UplinkFast, it affects all VLANs on the switch. You cannot configure UplinkFast on
an individual VLAN.
You can configure the UplinkFast 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 UplinkFast. This procedure is
optional.
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 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.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
spanning-tree uplinkfast
[
max-update-rate
pkts-per-second
]
Enable UplinkFast.
(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.
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.