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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 7 Configuring Spanning Tree
Configuring MISTP-PVST+ or MISTP on the Switch
entry is printed or when all the entries are associated to the same instance, the VLAN is mapped to that
instance. If two or more entries in the list are associated with different MISTP instances, the VLAN is
in conflict.
To clear up the conflict, you must manually remove the incorrect mapping(s) from the root switch. The
remaining entry on the list becomes the official mapping.
To determine VLAN mapping conflicts, perform this task in privileged mode:
This example shows that there is an attempt to map VLAN 2 to MISTP instance 1 and to MISTP
instance 3 on two different switches as seen from a third switch in the topology:
Console> (enable)
show spantree conflicts 2
Inst MAC Delay Time left
---- ----------------- --------- ---------
1 00-30-a3-4a-0c-00 inactive 20
3 00-30-f1-e5-00-01 inactive 10
The Delay timer shows the time in seconds remaining before the VLAN joins the instance. The field
displays
inactive
if the VLAN is already mapped to an instance (the timer has expired), or if the VLAN
is in conflict between instances.
The Time Left timer shows the time in seconds left before the entry expires and is removed from the
table. The timer is restarted every time an incoming BPDU confirms the mapping. Entries pertaining to
the root switch show
inactive
on the root switch itself.
The following examples are with VTP version 3 enabled. The root switch is also the primary server for
the nonroot switch. The root switch is not the primary server for the switch in conflict, because that
switch has been partitioned.
This example is from the root switch:
Console> (enable)
show spantree conflicts 1
No conflicts for vlan 1.
Inst MAC Delay Time left
---- ----------------- --------- ---------
1 00-05-31-40-64-00 inactive inactive
Console> (enable)
This example is from the nonroot switch:
Console> (enable)
show spantree conflicts 3
No conflicts for vlan 3.
Inst MAC Delay Time left
---- ----------------- --------- ---------
3 00-05-31-40-64-00 inactive 19
Console> (enable)
This example is from the switch in conflict (note that the switch is inactive):
Console> (enable)
show spantree conflicts 6
Inst MAC Delay Time left
---- ----------------- --------- ---------
6 00-05-31-40-64-00 inactive 18
5 00-09-7b-62-b0-80 inactive inactive
Console> (enable)
Task
Command
Determine VLAN mapping conflicts.
show spantree conflicts
vlan
