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Catalyst 6500 Series Switch Command Reference—Release8.4
OL-6244-01
Chapter2 Catalyst 6500 Series Switch and ROM Monitor Commands set spantree root
This command increases path costs to a value greater than 3000.
If you enable MISTP, you cannot set the VLAN root. If you enable PVST+, you cannot set the instance
root.
Examples This example shows how to set the primary root for a range of VLANs:
Console> (enable) set spantree root 1-10 dia 4
VLANs 1-10 bridge priority set to 8192
VLANs 1-10 bridge max aging time set to 14 seconds.
VLANs 1-10 bridge hello time set to 2 seconds.
VLANs 1-10 bridge forward delay set to 9 seconds.
Switch is now the root switch for active VLANs 1-6.
Console> (enable)
This example shows how to set the primary root for an instance:
Console> (enable) set spantree root mistp-instance 2-4 dia 4
Instances 2-4 bridge priority set to 8192
VLInstances 2-4 bridge max aging time set to 14 seconds.
Instances 2-4 bridge hello time set to 2 seconds.
Instances 2-4 bridge forward delay set to 9 seconds.
Switch is now the root switch for active Instances 1-6.
Console> (enable)
This example shows how to set the primary root for MST instance 5:
Console> (enable) set spantree root mst 5
Instance 5 bridge priority set to 24576.
Instance 5 bridge max aging time set to 16.
Instance 5 bridge hello time set to 2.
Instance 5 bridge forward delay set to 15.
Switch is now the root switch for active Instance 5.
Console> (enable)
This example shows how to set the secondary root for MST instance 0:
Console> (enable) set spantree root secondary mst 0
Instance 0 bridge priority set to 28672.
Instance 0 bridge max aging time set to 20.
Instance 0 bridge hello time set to 2.
Instance 0 bridge forward delay set to 15.
Console> (enable)
This example shows how to set the maximum number of bridges and the hello time of the root for MST
instance 0:
Console> (enable) set spantree root mst 0 dia 7 hello 2
Instance 0 bridge priority set to 24576.
Instance 0 bridge max aging time set to 20.
Instance 0 bridge hello time set to 2.
Instance 0 bridge forward delay set to 15.
Switch is now the root switch for active Instance 0.
Console> (enable)
These examples show that setting the bridge priority to 8192 was not sufficient to make this switch the
root. The priority was further reduced to 7192 (100 less than the current root switch) to make this switch
the root switch. However, reducing it to this value did not make it the root switch for active VLANs 16
and 17.
Console> (enable) set spantree root 11-20.
VLANs 11-20 bridge priority set to 7192
VLANs 11-10 bridge max aging time set to 20 seconds.