Setting The Pvst+ Bridge Id Priority - Cisco WS-C2948G-GE-TX Configuration Manual

Chapter 7 Configuring Spanning Tree
Table 7-4
Feature
VLAN 1
Enable state
MAC address reduction
Bridge priority
Bridge ID priority
Port priority
Port cost
Default spantree port cost
mode
Port VLAN priority
Port VLAN cost
Maximum aging time
Hello time
Forward delay time

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 0–65,535. The VLAN bridge ID priority becomes that value.
When the switch is in PVST+ mode with MAC address reduction enabled, you can enter one of 16 bridge
priority values: 0, 4096, 8192, 12,288, 16,384, 20,480, 24,576, 28,672, 32,768, 36,864, 40,960, 45,056,
49,152, 53,248, 57,344, or 61,440.
The switch creates the bridge ID priority by combining the VLAN bridge priority with the system ID
extension (the ID of the VLAN).
To set the spanning tree bridge priority for a VLAN, perform this task in privileged mode:
Task
Step 1 Set the bridge ID priority for a VLAN.
Step 2 Verify the bridge ID priority.
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
PVST+ Default Configuration
Default Value
All ports assigned to VLAN 1
PVST+ enabled for all VLANs
Disabled
32,768
32,769 (bridge priority plus system ID extension of VLAN 1)
32
Gigabit Ethernet: 4
•
• Fast Ethernet: 10
FDDI/CDDI: 10
•
• Ethernet: 100
Short (802.1D)
Same as port priority but configurable on a per-VLAN basis in PVST+
Same as port cost but configurable on a per-VLAN basis in PVST+
20 sec
2 sec
15 sec
Command
set spantree priority bridge_ID_priority [vlan]
show spantree [vlan] [active]
Using PVST+
7-23