1-15
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring STP
Configuring Spanning-Tree Features
Spanning-tree commands control the configuration of VLAN spanning-tree instances. You create a
spanning-tree instance when you assign an interface to a VLAN. The spanning-tree instance is removed
when the last interface is moved to another VLAN. You can configure switch and port parameters before
a spanning-tree instance is created; these parameters are applied when the spanning-tree instance is
created.
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.) In
Catalyst 3750-E-only and mixed switch stacks, all stack members run the same version of spanning tree.
For information about the different spanning-tree modes and how they interoperate, see the
“Spanning-Tree Interoperability and Backward Compatibility” section on page 1-11.
For configuration guidelines about UplinkFast, BackboneFast, and cross-stack UplinkFast, see the
“Optional Spanning-Tree Configuration Guidelines” section on page 1-12.
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. All stack members run the same
version of spanning-tree.
• Select pvst to enable PVST+ (the default setting).
• Select mst to enable MSTP (and RSTP). For more configuration
steps, see Chapter 1, “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.
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