Cisco Systems 3560 Manual De Usuario
19-9
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 19 Configuring Optional Spanning-Tree Features
Configuring Optional Spanning-Tree Features
Understanding 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 enabled on the entire
switched network. Loop guard prevents alternate and root ports from becoming designated ports, and
spanning tree does not send BPDUs on root or alternate ports.
failure that leads to a unidirectional link. This feature is most effective when it is enabled on the entire
switched network. Loop guard prevents alternate and root ports from becoming designated ports, and
spanning tree does not send BPDUs on root or alternate ports.
You can enable this feature by using the spanning-tree loopguard default global configuration
command.
command.
When the switch is operating in PVST+ or rapid-PVST+ mode, loop guard prevents alternate and root
ports from becoming designated ports, and spanning tree does not send BPDUs on root or alternate ports.
ports from becoming designated ports, and spanning tree does not send BPDUs on root or alternate ports.
When the switch is operating in MST mode, BPDUs are not sent on nonboundary ports only if the
interface is blocked by loop guard in all MST instances. On a boundary port, loop guard blocks the
interface in all MST instances.
interface is blocked by loop guard in all MST instances. On a boundary port, loop guard blocks the
interface in all MST instances.
Configuring Optional Spanning-Tree Features
These sections contain this configuration information:
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(optional)
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(optional)
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(optional)
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(optional)
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(optional)
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(optional)
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(optional)
Default Optional Spanning-Tree Configuration
shows the default optional spanning-tree configuration.
Table 19-1
Default Optional Spanning-Tree Configuration
Feature
Default Setting
Port Fast, BPDU filtering, BPDU guard
Globally disabled (unless they are individually configured
per interface).
per interface).
UplinkFast
Globally disabled.
BackboneFast
Globally disabled.
EtherChannel guard
Globally enabled.
Root guard
Disabled on all interfaces.
Loop guard
Disabled on all interfaces.