Juniper JUNOS OS 10.3 - SOFTWARE Manual page 1637

Example: Configuring Network Regions for VLANs with MSTP on EX Series Switches
Requirements
Overview and Topology
Copyright © 2010, Juniper Networks, Inc.
Multiple Spanning Tree Protocol (MSTP) is used to create a loop-free topology in networks
using multiple spanning tree regions, each region containing multiple spanning-tree
instances (MSTIs). MSTIs provide different paths for different VLANs. This functionality
facilitates better load sharing across redundant links.
Up to 64 MSTI instances can be created for an EX Series switch, and each MSTI can
support up to 4094 VLANs.
This example describes how to configure MSTP on four EX Series switches:
Requirements on page 1541
Overview and Topology on page 1541
Configuring MSTP on Switch 1 on page 1544
Configuring MSTP on Switch 2 on page 1547
Configuring MSTP on Switch 3 on page 1549
Configuring MSTP on Switch 4 on page 1552
Verification on page 1555
This example uses the following hardware and software components:
Junos OS Release 9.0 or later for EX Series switches
Four EX Series switches
Before you configure the switches for MSTP, be sure you have:
Installed the four switches. See "Connecting and Configuring an EX Series Switch
(J-Web Procedure)" on page 189.
Performed the initial software configuration on all switches. See Installing and
Connecting an EX3200 or EX4200 Switch.
When the number of VLANs grows in a network, MSTP provides a more efficient way of
creating a loop-free topology using MSTIs. Each MSTI in the spanning tree domain
maintains its own tree. Each tree can be mapped to different links, utilizing bandwidth
that would be unavailable to a single tree. MSTIs reduce demand on system resources.
Chapter 65: Examples of Spanning-Tree Protocols Configuration
1541