Configuring Mstp Regions; Selecting A Spanning Tree Protocol; Using Mstp; Table 10: Selecting A Spanning Tree Protocol - Juniper EX9200 Features Manual

Configuring MSTP Regions

Selecting a Spanning Tree Protocol

Table 10: Selecting a Spanning Tree Protocol

Protocol Advantages
RSTP Rapid Spanning Tree Protocol is the default switch
configuration and is recommended for most network
configurations because it converges more quickly
than STP after a failure.
Voice and video work better with RSTP than they
do with STP.
RSTP is backward compatible with STP; therefore,
switches do not all have to run RSTP.
Copyright © 2017, Juniper Networks, Inc.
single topology that connects all switches (STP, RSTP, and MSTP devices) through an
active topology, ensuring connectivity between LANs and devices within a bridged network.
This functionality provided by MSTP enables you to better utilize network resources while
remaining backward-compatible with older network devices.
When enabling MSTP, you define one or more MSTP regions. An MSTP region defines a
logical domain where multiple spanning-tree instances (MSTIs) can be administered
independently of MSTIs in other regions, setting the boundary for bridge protocol data
units (BPDUs) sent by one MSTI. An MSTP region is a group of switches that is defined
by three parameters:
Region name—User-defined alphanumeric name for the region.
Revision level—User-defined value that identifies the region.
Mapping table—Numerical digest of VLAN-to-instance mappings.
An MSTP region can support up to 64 MSTIs,, and each MSTI can support from 1 to 4094
VLANs. When you define a region, MSTP automatically creates an internal spanning-tree
instance (IST instance 0) that provides the root switch for the region and includes all
currently configured VLANs that are not specifically assigned to a user-defined MSTI. An
MSTI includes all static VLANs that you specifically add to it. The switch places any
dynamically created VLANs in the IST instance by default, unless you explicitly map them
to another MSTI. Once you assign a VLAN to a user-defined MSTI, the switch removes
the VLAN from the IST instance.
The default factory configuration for EX Series switches is RSTP, a faster version of STP.
To determine which spanning-tree protocol is best for your situation, see
Table 10 on page 79 below.
Disadvantages
RSTP does not work with 802.1D 1998 bridges.
RSTP is not recommended for multiple VLAN
networks because it is not VLAN-aware—as a result,
all VLANs within a LAN share the same
spanning-tree. This limits the number of forwarding
paths for data traffic.
Chapter 4: Using MSTP
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