8-16
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
78-13315-02
Chapter 8 Configuring Spanning Tree
Using PVST+
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 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
]