Cisco Systems 2960 Manual De Usuario
16-13
Catalyst 2960 and 2960-S Switch Software Configuration Guide
OL-8603-09
Chapter 16 Configuring STP
Configuring Spanning-Tree Features
Default Spanning-Tree Configuration
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.
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
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
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.
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.
Caution
Switches that are not running spanning tree still forward BPDUs that they receive so that the other
switches on the VLAN that have a running spanning-tree instance can break loops. Therefore, spanning
tree must be running on enough switches to break all the loops in the network; for example, at least one
switches on the VLAN that have a running spanning-tree instance can break loops. Therefore, spanning
tree must be running on enough switches to break all the loops in the network; for example, at least one
Table 16-3
Default Spanning-Tree Configuration
Feature
Default Setting
Enable state
Enabled on VLAN 1.
For more information, see the
Spanning-tree mode
PVST+. (Rapid PVST+ and MSTP are
disabled.)
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