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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 7 Configuring Spanning Tree
Configuring PVST+ on the Switch
Setting the PVST+ Bridge ID Priority
The bridge ID priority is the priority of a VLAN when the switch is in PVST+ mode.
When the switch is in PVST+ mode without MAC address reduction enabled, you can enter a bridge
priority value between 0–65535. The bridge priority value that you enter also becomes the VLAN bridge
ID priority for that VLAN.
When the switch is in PVST+ mode with MAC address reduction enabled, you can enter one of 16 bridge
priority values: 0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152,
53248, 57344, or 61440.
The bridge priority is combined with the system ID extension (that is, the ID of the VLAN) to create the
bridge ID priority for the VLAN.
To set the spanning-tree bridge priority for a VLAN, perform this task in privileged mode:
This example shows how to set the PVST+ bridge ID priority when MAC address reduction is not
enabled (default):
Console> (enable)
set spantree priority 30000 1
Spantree 1 bridge priority set to 30000.
Console> (enable)
show spantree 1
VLAN 1
Spanning tree mode PVST+
Spanning tree type ieee
Spanning tree enabled
Designated Root 00-60-70-4c-70-00
Designated Root Priority 16384
Designated Root Cost 19
Designated Root Port 2/3
Root Max Age 14 sec Hello Time 2 sec Forward Delay 10 sec
Bridge ID MAC ADDR 00-d0-00-4c-18-00
Bridge ID Priority 30000
Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Port Vlan Port-State Cost Prio Portfast Channel_id
------------------------ ---- ------------- --------- ---- -------- ----------
1/1 1 not-connected 4 32 disabled 0
1/2 1 not-connected 4 32 disabled 0
2/1 1 not-connected 100 32 disabled 0
2/2 1 not-connected 100 32 disabled 0
This example shows how to set the PVST+ bridge ID priority when MAC reduction is enabled:
Console> (enable)
set spantree priority 32768 1
Spantree 1 bridge ID priority set to 32769
(bridge priority: 32768 + sys ID extension: 1)
Console> (enable)
show spantree 1/1 1
VLAN 1
Spanning tree mode PVST+
Spanning tree type ieee
Spanning tree enabled
Task
Command
Step 1
Set the PVST+ bridge ID priority for a VLAN.
set spantree priority
bridge_ID_priority
[
vlan
]
Step 2
Verify the bridge ID priority.
show spantree
[
vlan
] [
active
]