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Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 21 Configuring MSTP
How to Configure MSTP

Restarting the Protocol Migration Process

A switch running MSTP supports a built-in protocol migration mechanism that enables it to interoperate
with legacy IEEE 802.1D switches. If this switch receives a legacy IEEE 802.1D configuration BPDU
(a BPDU with the protocol version set to 0), it sends only IEEE 802.1D BPDUs on that port. An MSTP
switch also can detect that a port is at the boundary of a region when it receives a legacy BPDU, an MST
BPDU (Version 3) associated with a different region, or an RST BPDU (Version 2).
However, the switch does not automatically revert to the MSTP mode if it no longer receives
IEEE 802.1D BPDUs because it cannot detect whether the legacy switch has been r emoved from the link
unless the legacy switch is the designated switch. A switch also might contin ue to assign a boundary role
to a port when the switch to which it is connected has joined the region.
How to Configure MSTP

Specifying the MST Region Configuration and Enabling MSTP

This task is required.
Command Purpose
Step 1 configure terminal Enters global configuration mode.
Step 2 spanning-tree mst configuration Enters MST configuration mode.
Step 3 instance instance-id vlan vlan-range Maps VLANs to an MST instance.
instance-id—range is 0 to 4096.
vlan vlan-range—range is 1 to 4096.
When you map VLANs to an MST instance, the mapping is
incremental, and the VLANs specified in the command are added to
or removed from the VLANs that were previously mapped.
To specify a VLAN range, use a hyphen; for example, instance 1 vlan
1-63 maps VLANs 1 through 63 to MST instance 1.
To specify a VLAN series, use a comma; for example, instance 1 vlan
10, 20, 30 maps VLANs 10, 20, and 30 to MST instance 1.
Step 4 name name Specifies the configuration name. The name string has a maximum length
of 32 characters and is case sensitive.
Step 5 revision version Specifies the configuration revision number. The range is 0 to 65535.
Step 6 show pending Verifies your configuration by displaying the pending configuration.
Step 7 exit Applies all changes, and returns to global configuration mode.