Disabling Mistp-Pvst+ Or Mistp; Configuring A Root Switch; Configuring A Primary Root Switch - Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual

Chapter 8 Configuring Spanning Tree

Disabling MISTP-PVST+ or MISTP

When the switch is in MISTP mode, you disable spanning tree on an instance, not for the whole switch.
When you disable spanning tree on an MISTP instance, the instance still exists on the switch, all of the
VLANs mapped to it have all of their ports forwarding, and the instance BPDUs are flooded.
To disable an MISTP instance, perform this task in privileged mode:
Task
Disable an MISTP instance.
This example shows how to disable an MISTP instance:
Console> (enable) set spantree disable mistp-instance 2
MI-STP instance 2 disabled.

Configuring a Root Switch

These sections explain how to configure a root switch:
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Configuring a Primary Root Switch

You can set a root switch on a VLAN when the switch is in PVST+ mode or on an MISTP instance when
the switch is in MISTP mode. You enter the set spantree root command to reduce the bridge priority
(the value associated with the switch) from the default (32768) to a lower value, which allows the switch
to become the root switch.
When you specify a switch as the primary root, the default bridge priority is modified so that it becomes
the root for the specified VLANs. The switch checks the bridge priority of the current root switches for
each VLAN. The bridge priority for the specified VLANs is set to 8192 if this value will cause the switch
to become the root for the specified VLANs. If any root switch for the specified VLANs has a bridge
priority lower than 8192, the switch sets the bridge priority for the specified VLANs to 1 less than the
lowest bridge priority. Because different VLANs could potentially have different root switches, the
bridge VLAN-priority chosen makes this switch the root for all the VLANs that are specified. If reducing
the bridge priority as low as 1 still does not make the switch the root switch, the system displays a
message.
Enter the set spantree root command on backbone switches or distribution switches only, not on
Caution
access switches.
To configure a switch as the primary root switch, perform this task in privileged mode:
78-13315-02
Configuring a Primary Root Switch, page 8-31
Configuring a Secondary Root Switch, page 8-32
Configuring a Root Switch to Improve Convergence, page 8-33
Using Root Guard—Preventing Switches from Becoming Root, page 8-34
Command
set spantree disable mistp-instance instance [all]
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4

Configuring a Root Switch

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