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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
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Chapter19 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Enabling Root Guard
Root guard enabled on an interface applies to all the VLA Ns t o whi ch t h e i nter face bel ongs . D o no t
enable the root guard on interfaces to be used by the UplinkFast feature. With UplinkFast, the backup
interfaces (in the blocked state) replace the root port in the ca se of a fa ilur e. However, if root guard is
also enabled, all the backup interfaces used by the UplinkFast feature are placed in the root-in consisten t
state (blocked) and are prevented from reaching the forwarding state.
Note You cannot enable both root guard and loop guard at the same time.
You can enable this feature if your switch is running PVST+, rapid PVST+, or MST P.
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface. This
procedure is optional.
To disable root guard, use the no spanning-tree guard interface configuration command.
Enabling Loop Guard
You can use loop guard to prevent alternate or root ports from becoming designated ports b eca use o f a
failure that leads to a unidirectional link. This feature is most effective when it is conf igured on th e entire
switched network. Loop guard operates only on interfaces that are considered poin t-to-p oint by the
spanning tree.
Note You cannot enable both loop guard and root guard at the same time.
You can enable this feature if your switch is running PVST+, rapid PVST+, or MST P.
Beginning in privileged EXEC mode, follow these steps to enable loop guard. This procedure is optional.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify an interface to configure, and enter interface configuration mode.
Step3 spanning-tree guard root Enable root guard on the interface.
By default, root guard is disabled on all interfaces.
Step4 end Return to privileged EXEC mode.
Step5 show running-config Verify your entries.
Step6 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step1 show spanning-tree active
or
show spanning-tree mst
Verify which interfaces are alternate or root ports.
Step2 configure terminal Enter global configuration mode.