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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 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 Table 9-2. Disable STP only if you are sure there are no loops in the network topology.
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 basis:
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 seconds.
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.
Table 9-2 Default STP Configuration (continued)
Feature Default Setting
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
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 zeroes.
Step 3
end Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
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