Cisco WS-C2980G-A Software Guide - Page 135

Disabling MISTP-PVST+ or MISTP, Configuring a Root Switch

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Chapter 7 Configuring Spanning Tree Configuring a Root Switch Unmapping VLANs from an MISTP Instance The keyword none is used to unmap the specified VLANs from the MISTP instances to which they are currently mapped. When you unmap a VLAN from an MISTP instance, the resulting state of all the ports of the VLAN (if the VLAN exists) is blocking. To unmap a VLAN or all VLANs from an MISTP instance, perform this task in privileged mode: Task Unmap a VLAN from an MISTP instance. Command set vlan vlan mistp-instance none This example shows how to unmap a VLAN from an MISTP instance: Console> (enable) set vlan 6 mistp none Vlan 6 configuration successful 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. Command set spantree disable mistp-instance instance [all] 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 This section explains how to configure a primary root switch and a secondary root switch, and how to prevent a switch from becoming a root switch using the root guard feature. 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. Enter the set spantree root command to lower the bridge priority (the value that is associated with the switch) below the default (32,768); the switch can then become the root switch. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 7-39

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7-39
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
Release 8.1
78-15486-01
Chapter 7
Configuring Spanning Tree
Configuring a Root Switch
Unmapping VLANs from an MISTP Instance
The keyword
none
is used to unmap the specified VLANs from the MISTP instances to which they are
currently mapped. When you unmap a VLAN from an MISTP instance, the resulting state of all the ports
of the VLAN (if the VLAN exists) is
blocking
.
To unmap a VLAN or all VLANs from an MISTP instance, perform this task in privileged mode:
This example shows how to unmap a VLAN from an MISTP instance:
Console> (enable)
set vlan 6 mistp none
Vlan 6 configuration successful
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:
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
This section explains how to configure a primary root switch and a secondary root switch, and how to
prevent a switch from becoming a root switch using the root guard feature.
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. Enter the
set spantree root
command to lower the bridge priority (the
value that is associated with the switch) below the default (32,768); the switch can then become the root
switch.
Task
Command
Unmap a VLAN from an MISTP instance.
set vlan
vlan
mistp-instance none
Task
Command
Disable an MISTP instance.
set spantree disable mistp-instance
instance
[
all
]