Using Vstp; Understanding Vstp For Ex Series Switches And Qfx Series Switches; Chapter 7 Using Vstp - Juniper EX9200 Features Manual

CHAPTER 7

Using VSTP

Understanding VSTP for EX Series Switches and QFX Series Switches

Copyright © 2017, Juniper Networks, Inc.
Understanding VSTP for EX Series Switches and QFX Series Switches on page 159
Configuring a Spanning-Tree Instance Interface as an Edge Port for Faster
Convergence on page 161
RSTP or VSTP Forced to Run as IEEE 802.1D STP on page 162
Forcing RSTP or VSTP to Run as IEEE 802.1D STP (CLI Procedure) on page 162
Configuring Spanning Tree Protocols (J-Web Procedure) on page 163
Configuring VLAN Spanning Tree Protocol on page 168
Reverting to RSTP or VSTP from Forced IEEE 802.1D STP on page 170
Juniper Networks EX Series Ethernet Switches provide Layer 2 loop prevention through
Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), Multiple Spanning
Tree Protocol (MSTP), and VLAN Spanning Tree Protocol (VSTP). The default factory
configuration for EX Series switches uses RSTP. If you use VLANs, however, we
recommend that you enable MSTP unless your network requires the device compatibility
provided by VSTP. Switches configured to run VSTP automatically assign each VLAN to
one spanning-tree instance that runs RSTP. While this approach is useful to optimize
network usage in small networks with a limited number of VLANs, a VSTP configuration
in a network with several hundred VLANs can overload switch CPUs. MSTP ensures that
your network is not slowed down by the increased network traffic caused by hundreds
of VLANs, each with its own spanning-tree instance.
VSTP and RSTP are the only spanning-tree protocols that can be configured concurrently
on a switch. The maximum number of VLANs that can be supported by VSTP depends
upon whether you are using Junos OS for EX Series and QFX Series switches with support
for the Enhanced Layer 2 Software (ELS) configuration style or Junos OS that does not
support ELS. For ELS details, see Getting Started with Enhanced Layer 2 Software. For
additional VLANs, use RSTP.
On EX Series (except EX9200) and QFX Series switches running Junos OS that supports
ELS—VSTP can support up to 510 VLANs.
On EX9200 switches—VSTP can support up to 4000 VLANs.
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