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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 17 Configuring STP
Configuring Spanning-Tree Features
The switch supports PVST+, rapid PVST+, and MSTP, but only one version can be active at any time.
(For example, all VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.) For
information about the different spanning-tree modes and how they interoperate, see the “Spanning-Tree
Interoperability and Backward Compatibility” section on page 17-10.
For configuration guidelines about UplinkFast and BackboneFast, see the “Optional Spanning-Tree
Configuration Guidelines” section on page 19-10.
Caution Loop guard works only on point-to-point links. We recommend that each end of the link has a directly
connected device that is running STP.
Changing the Spanning-Tree Mode.
The switch supports three spanning-tree modes: PVST+, rapid PVST+, or MSTP. By default, the switch
runs the PVST+ protocol.
Beginning in privileged EXEC mode, follow these steps to change the spanning-tree mode. If you want
to enable a mode that is different from the default mode, this procedure is required.
Command Purpose
Step 1 configure terminal Enter global configuration mode.
Step 2 spanning-tree mode {pvst | mst |
rapid-pvst}
Configure a spanning-tree mode.
Select pvst to enable PVST+ (the default setting).
Select mst to enable MSTP (and RSTP). For more configuration
steps, see Chapter 18, “Configuring MSTP.
Select rapid-pvst to enable rapid PVST+.
Step 3 interface interface-id (Recommended for rapid-PVST+ mode only) Specify an interface to
configure, and enter interface configuration mode. Valid interfaces
include physical ports, VLANs, and port channels. The VLAN ID range
is 1 to 4094. The port-channel range is 1 to 48.
Step 4 spanning-tree link-type point-to-point (Recommended for rapid-PVST+ mode only) Specify that the link type
for this port is point-to-point.
If you connect this port (local port) to a remote port through a
point-to-point link and the local port becomes a designated port, the
switch negotiates with the remote port and rapidly changes the local
port to the forwarding state.
Step 5 end Return to privileged EXEC mode.
Step 6 clear spanning-tree detected-protocols (Recommended for rapid-PVST+ mode only) If any port on the switch
is connected to a port on a legacy IEEE 802.1D switch, restart the
protocol migration process on the entire switch.
This step is optional if the designated switch detects that this switch is
running rapid PVST+.