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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter10 Configuring STP
Configuring Basic STP Features
Disabling STP
STP is enabled by default on VLAN 1 and on all newly created VLANs up to the spanning-tree limit
specified in Table10-3. Disable ST P on ly if yo u are sure ther e a re no l oo ps in the n etwor k topol ogy.
Caution When STP is disabled and loops are present in the topology, excessive traffic and indefinite packet
duplication can drastically reduce network performance.
Beginning in privileged EXEC mode, follow these steps to disable STP on a per-VLAN ba sis:
To re-enable STP, use the spanning-tree vlan vlan-id global configuration command.
Configuring the Root Switch
The switch maintains a separate spanning-tree instance for each active VLAN configured on it. A bridge
ID, consisting of the switch priority and the switch MAC address, is associated with each instance. For
each VLAN, the switch with the lowest bridge ID becomes the root switch for that VLAN.
Forward-delay time 15 se conds.
Maximum-aging time 20 seconds.
Port Fast Disabled on all interfaces.
BPDU guard Disabled on the switch.
UplinkFast Disabled on the switch.
BackboneFast Disabled on the switch.
Root guard Disabled on all interfaces.
EtherChannel guard Enabled on the switch.
Table10-3 Default STP Configuration (continued)
Feature Default Setting
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 no spanning-tree vlan vlan-id Disable STP on a per-VLAN basis.
For vlan-id, the range is 1 to 1005. Do not enter leading zeros.
Step3 end Return to privileged EXEC mode.
Step4 show spanning-tree vlan vlan-id Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.