CHAPTER
10-1
Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
10
Configuring MSTP
This chapter describes how to configure the Cisco implementation of the IEEE 802.1s Multiple STP
(MSTP) on your Cisco Systems Intelligent Gigabit Ethernet Switch Module.
The MSTP enables multiple VLANs to be mapped to the same spanning-tree instance, reducing the
number of spanning-tree instances needed to support a large number of VLANs. The MSTP provides for
multiple forwarding paths for data traffic and enables load balancing. It improves the fault tolerance of
the network because a failure in one instance (forwarding path) does not affect other instances
(forwarding paths). The most common initial deployment of MSTP is in the backbone and distribution
layers of a Layer 2 switched network. This deployment provides the highly available network required
in a service-provider environment.
When the switch is in the MST mode, the Rapid Spanning Tree Protocol (RSTP), which is based on
IEEE 802.1w, is automatically enabled. The RSTP provides rapid convergence of the spanning tree
through explicit handshaking that eliminates the IEEE 802.1D forwarding delay and quickly transitions
root ports and designated ports to the forwarding state.
Both MSTP and RSTP improve the spanning-tree operation and maintain backward-compatibility with
equipment that is based on the (original) IEEE 802.1D spanning tree, with existing Cisco-proprietar y
Multiple Instance STP (MISTP) and with existing Cisco per-VLAN spanning-tree plus (PVST+) and
rapid per-VLAN spanning-tree plus (rapid PVST+). For information about PVST+ and rapid PVST+,
see Chapter9, “Configuring STP.” For information about other spanning-tree features such as Port Fast,
UplinkFast, root guard, and so forth, see Chapter 11, “Configu ring Optional Spanning-Tree Features.”
Note For complete syntax and usage information for the commands used in this chapter, see the command
reference for this release.
This chapter consists of these sections:
Understanding MSTP, page 10-2
Understanding RSTP, page 10-5
Configuring MSTP Features, page 10-10
Displaying the MST Configuration and Status, page 10-22