Disabling Spanning Tree; Configuring The Root Switch - Cisco Catalyst 3750-X Software Configuration Manual

Chapter 20 Configuring STP
Command
Step 6
clear spanning-tree detected-protocols
Step 7
show spanning-tree summary
and
show spanning-tree interface
interface-id
Step 8
copy running-config startup-config
To return to the default setting, use the no spanning-tree mode global configuration command. To return
the port to its default setting, use the no spanning-tree link-type interface configuration command.

Disabling Spanning Tree

Spanning tree is enabled by default on VLAN 1 and on all newly created VLANs up to the spanning-tree
limit specified in the
only if you are sure there are no loops in the network topology.
When spanning tree is disabled and loops are present in the topology, excessive traffic and indefinite
Caution
packet duplication can drastically reduce network performance.
Beginning in privileged EXEC mode, follow these steps to disable spanning-tree on a per-VLAN basis.
This procedure is optional.
Command
Step 1
configure terminal
Step 2
no spanning-tree vlan vlan-id
Step 3
end
Step 4 show spanning-tree vlan vlan-id
Step 5
copy running-config startup-config
To re-enable spanning-tree, 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.
OL-21521-01
Purpose
(Recommended for rapid-PVST+ mode only) If any port on the switch
is connected to a port on a legacy IEEE 802.1D switch, restart the
protocol migration process on the entire switch.
This step is optional if the designated switch detects that this switch is
running rapid PVST+.
Verify your entries.
(Optional) Save your entries in the configuration file.
"Supported Spanning-Tree Instances" section on page
Purpose
Enter global configuration mode.
For vlan-id, the range is 1 to 4094.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
Configuring Spanning-Tree Features
20-10. Disable spanning tree
20-15