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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 11 Configuring STP
Configuring Spanning-Tree Features
• Configuring the Hello Time, page 11-19
• Configuring the Forwarding-Delay Time for a VLAN, page 11-19
• Configuring the Maximum-Aging Time for a VLAN, page 11-20
• Configuring STP for Use in a Cascaded Stack, page 11-20
Default STP Configuration
Table 11-3 shows the default STP configuration.
STP Configuration Guidelines
If more VLANs are defined in the VTP than there are spanning-tree instances, you can enable STP on
only 64 VLANs. If the number of VLANs exceeds 64, we recommend that you enable the MSTP to map
multiple VLANs to a single spanning-tree instance. For more information, see the Chapter 12,
“Configuring RSTP and MSTP.”
If 64 instances of spanning tree are already in use, you can disable STP 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 STP on a specific VLAN, and use the spanning-tree vlan vlan-id
global configuration command to enable STP on the desired VLAN.
Table 11-3 Default STP Configuration
Feature Default Setting
Enable state Enabled on VLAN 1.
Up to 64 spanning-tree instances can be
enabled.
Switch priority 32768.
Spanning-tree port priority (configurable on a per-interface basis—used on
interfaces configured as Layer 2 access ports)
128.
Spanning-tree port cost (configurable on a per-interface basis—used on
interfaces configured as Layer 2 access ports)
1000 Mbps: 4.
100 Mbps: 19.
10 Mbps: 100.
Spanning-tree VLAN port priority (configurable on a per-VLAN basis—used on
interfaces configured as Layer 2 trunk ports)
128.
Spanning-tree VLAN port cost (configurable on a per-VLAN basis—used on
interfaces configured as Layer 2 trunk ports)
1000 Mbps: 4.
100 Mbps: 19.
10 Mbps: 100.
Hello time 2 seconds.
Forward-delay time 15 seconds.
Maximum-aging time 20 seconds.