Cisco 2975 - Catalyst LAN Base Switch, Руководство по настройке программного обеспечения

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18-19
Catalyst 2975 Switch Software Configuration Guide
OL-19720-02
Chapter 18 Configuring Optional Spanning-Tree Features
Displaying the Spanning-Tree Status
Enabling Loop Guard
You can use loop guard to prevent alternate or root ports from becoming designated ports because of a
failure that leads to a unidirectional link. This feature is most effective when it is configured on the entire
switched network. Loop guard operates only on interfaces that are considered point-to-point 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 MSTP.
Beginning in privileged EXEC mode, follow these steps to enable loop guard. This procedure is optional.
To globally disable loop guard, use the no spanning-tree loopguard default global configuration
command. You can override the setting of the no spanning-tree loopguard default global configuration
command by using the spanning-tree guard loop interface configuration command.
Displaying the Spanning-Tree Status
To display the spanning-tree status, use one or more of the privileged EXEC commands in Table 18-2 :
Command Purpose
Step 1 show spanning-tree active
or
show spanning-tree mst
Verify which interfaces are alternate or root ports.
Step 2 configure terminal Enter global configuration mode.
Step 3
spanning-tree loopguard default Enable loop guard.
By default, loop guard is disabled.
Step 4 end Return to privileged EXEC mode.
Step 5
show running-config Verify your entries.
Step 6 copy running-config startup-config (Optional) Save your entries in the configuration file.
Table 18-2 Commands for Displaying the Spanning-Tree Status
Command Purpose
show spanning-tree active Displays spanning-tree information on active interfaces only.
show spanning-tree detail Displays a detailed summary of interface information.
show spanning-tree interface interface-id Displays spanning-tree information for the specified interface.
show spanning-tree mst interface interface-id Displays MST information for the specified interface.
show spanning-tree summary [ totals ] Displays a summary of interface states or displays the total lines of the
spanning-tree state section.