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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter16 Configuring Optiona l Spa nning-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 th e pa th co st r ed u ces the chance that
the 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
Before enabling CSUF, make sure your stack switches are properly connected. For more information,
see the “Connecting the Stack Ports” section on page 16-8.
You can enable the CSUF 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 CSUF. This procedure is optional.
Step4 show spanning-tree summary Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 spanning-tree uplinkfast [max-update-rate
pkts-per-second]Enable UplinkFast on the switch.
(Optional) For max-update-rate pkts-per-second, specify the
number of packets per second at which update packets are sent. The
range is 0 to 65535; the default is 150 packets per second.
Step3 interface interface-id Specify the GBIC module interface on which to enable CSUF, and
enter interface configuration mode.
Step4 spanning-tree stack-port Enable CSUF on only one stack-port GBIC interface.
The stack port connects to the GigaStack GBIC module multidrop
backbone. If you try to enable CSUF on a Fast Ethernet or a
Gigabit-capable Ethernet port, you receive an error message .
If CSUF is already enabled on an interface and you tr y to e nab le it
on another interface, you receive an error messag e. Y ou mu st disable
CSUF on the first interface before enabling it on a new interface.
Use this command only on access switches.
Step5 end Return to privileged EXEC mode.
Step6 show running-config Verify your entries.
Step7 copy running-config startup-config (Optional) Save your entries in the configuration file.