MSTP was originally defined in the IEEE 802.1s draft specification and later incorporated
into the IEEE 802.1Q-2003 specification.
Related
Documentation
Understanding STP for EX Series Switches on page 1519
•
•
Understanding RSTP for EX Series Switches on page 1520
•
Understanding Layer 2 Protocol Tunneling on EX Series Switches on page 1299
•
Example: Configuring Network Regions for VLANs with MSTP on EX Series Switches
on page 1541
Understanding BPDU Protection for STP, RSTP, and MSTP on EX Series Switches
Juniper Networks EX Series Ethernet Switches provide Layer 2 loop prevention through
Spanning Tree Protocol (STP), Rapid Spanning Tree Protocol (RSTP), VLAN Spanning
Tree Protocol (VSTP), and Multiple Spanning Tree Protocol (MSTP). BPDU protection
can help prevent STP misconfigurations that can lead to network outages.
A loop-free network is supported through the exchange of a special type of frame called
bridge protocol data unit (BPDU). Receipt of BPDUs on certain interfaces in an STP,
RSTP, VSTP, or MSTP topology, however, can lead to network outages. Enable BPDU
protection on those interfaces to prevent these outages.
Peer STP applications running on the switch interfaces use BPDUs to communicate.
Ultimately, the exchange of BPDUs determines which interfaces block traffic and which
interfaces become root ports and forward traffic.
However, a user bridge application running on a PC can also generate BPDUs. If these
BPDUs are picked up by STP applications running on the switch, they can trigger STP
miscalculations, and those miscalculations can lead to network outages.
Enable BPDU protection on switch interfaces connected to user devices or on interfaces
on which no BPDUs are expected, such as edge ports. If BPDUs are received on a protected
interface, the interface is disabled and stops forwarding frames.
Not only can you configure BPDU protection on a switch with a spanning tree, but also
on a switch without a spanning tree. This type of topology typically consists of a non-STP
switch connected to an STP switch through a trunk interface.
To configure BPDU protection on a switch with a spanning tree, include the
bpdu-block-on-edge
statement at the [
edit protocols
(
stp
|
mstp
|
rstp
)] hierarchy level.
To configure BPDU protection on a switch without a spanning tree, include the
bpdu-block
statement at the [
edit ethernet-switching-options interface interface-name
] hierarchy
level.
After the misconfiguration that triggered the BPDUs being sent to an interface is fixed in
the topology, the interface can be unblocked in one of two ways:
•
If the
disable-timeout
statement has been included in the BPDU configuration, the
interface automatically returns to service after the timer expires.
•
Use the operational mode command
clear ethernet-switching bpdu-error
.
Copyright © 2010, Juniper Networks, Inc.
1522
Complete Software Guide for Junos
®
OS for EX Series Ethernet Switches, Release 10.3
Summary of Contents for JUNOS OS 10.3 - SOFTWARE
Page 325: ...CHAPTER 17 Operational Mode Commands for System Setup 229 Copyright 2010 Juniper Networks Inc ...
Page 1323: ...CHAPTER 56 Operational Mode Commands for Interfaces 1227 Copyright 2010 Juniper Networks Inc ...
Page 2841: ...CHAPTER 86 Operational Commands for 802 1X 2745 Copyright 2010 Juniper Networks Inc ...
Page 3367: ...CHAPTER 113 Operational Mode Commands for CoS 3271 Copyright 2010 Juniper Networks Inc ...
Page 3435: ...CHAPTER 120 Operational Mode Commands for PoE 3339 Copyright 2010 Juniper Networks Inc ...
Page 3529: ...CHAPTER 126 Operational Mode Commands for MPLS 3433 Copyright 2010 Juniper Networks Inc ...
