Changing The Spanning-Tree Mode - Cisco Catalyst 3750 Software Configuration Manual

Chapter 14 Configuring STP
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.) For
information about the different spanning-tree modes and how they interoperate, see the
Interoperability and Backward Compatibility" section on page
The UplinkFast and BackboneFast features are not supported with the rapid PVST+.

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
Step 1
configure terminal
Step 2
spanning-tree mode {pvst | mst |
rapid-pvst}
Step 3
interface interface-id
Step 4 spanning-tree link-type point-to-point
Step 5 end
Step 6 clear spanning-tree detected-protocols
78-15870-01
Purpose
Enter global configuration mode.
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 15, "Configuring MSTP."
Select rapid-pvst to enable rapid PVST+.
•
(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 12.
(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 transitions the local
port to the forwarding state.
Return to privileged EXEC mode.
(Recommended for rapid-PVST+ mode only) If any port on the switch
is connected to a port on a legacy 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+.
Catalyst 3750 Metro Switch Software Configuration Guide
Configuring Spanning-Tree Features
"Spanning-Tree
14-10.
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