18-13
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter18 Configuring STP
Configuring Spanning-Tree Features
Configuring the Switch Priority of a VLAN, page18-21 (optional)
Configuring Spanning-Tree Timers, page18-22 (optional)
Default Spanning-Tree Configuration
Table18-3 shows the default spanning-tree configuration.
Spanning-Tree Configuration Guidelines
Each stack member runs its own spanning tree, and the entire stack appears as a single switch to the rest
of the network.
If more VLANs are defined in the VTP than there are spanning-tree instances, you can enable PVST+
or rapid PVST+ on only 128 VLANs on each switch stack. The remaining VLANs operate with spanning
tree disabled. However, you can map multiple VLANs to the same spanning-tree instances by using
MSTP. For more information, see Chapter19, “Configuring MSTP.”
If 128 instances of spanning tree are already in use, you can disable spanning tree on one of the VLANs
and then enable it on the VLAN where you want it to run. Use the no spanning-tree vlan vlan-id global
configuration command to disable spanning tree on a specific VLAN, and use the spanning-tree vlan
vlan-id global configuration command to enable spanning tree on the desired VLAN.
Table18-3 Default Spanning-Tree Configuration
Feature Default Setting
Enable state Enabled on VLAN 1.
For more information, see the “Supported
Spanning-Tree Instances” section on
page 18-10.
Spanning-tree mode PVST+. (Rapid PVST+ and MSTP are
disabled.)
Switch priority 32768.
Spanning-tree port priority (configurable on a per-interface basis) 128.
Spanning-tree port cost (configurable on a per-interface basis) 1000 Mb/s: 4.
100 Mb/s: 19.
10 Mb/s: 100.
Spanning-tree VLAN port priority (configurable on a per-VLAN basis) 128.
Spanning-tree VLAN port cost (configurable on a per-VLAN basis) 1000 Mb/s: 4.
100 Mb/s: 19.
10 Mb/s: 100.
Spanning-tree timers Hello time: 2 seconds.
Forward-delay time: 15 seconds.
Maximum-aging time: 20 seconds.
Transmit hold count: 6 BPDUs