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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 20 Configuring STP
How to Configure STP
You can prevent this possibility by setting up allowed lists on the trunk ports of switches that have used
up their allocation of spanning-tree instances. Setting up allowed lists is not necessary in many cases and
can make it more labor-intensive to add another VLAN to the network.
Spanning-tree commands control the configuration of VLAN spanni ng-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.) For
information about the different spanning-tree modes and how they interoperate, see the “Spanning-Tree
Interoperability and Backward Compatibility” section on page 20-10.
For configuration information about UplinkFast and BackboneFast, see the “Information About
Configuring the Optional Spanning-Tree Features” section on page 22-1.
Caution Loop guard works only on point-to-point links. We recommend that eac h end of the link has a directly
connected device that is running STP.
How to Configure STP

Changing the Spanning-Tree Mode

Command Purpose
Step 1 configure terminal Enters global configuration mode.
Step 2 spanning-tree mode {pvst | mst |
rapid-pvst}
Configures a spanning-tree mode.
• pvst—Enables PVST+ (the default setting).
• mst—Enables MSTP (and RSTP). For more configuration steps,
see Chapter 21, “Configuring MSTP.”
• rapid-pvst—Enables rapid PVST+.
Step 3 interface interface-id (Recommended for rapid-PVST+ mode only) Specifies an interface to
configure, and enters interface configuration mode. Valid interfaces
include physical ports, VLANs, and port channels.
Step 4 spanning-tree link-type point-to-point (Recommended for rapid-PVST+ mode only) Specifies 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.