Switches - Juniper JUNOS OS 10.3 - SOFTWARE Manual

Complete Software Guide for Junos
Related
Documentation
Understanding BPDU Protection for STP, RSTP, and MSTP on EX Series Switches
1522
®
OS for EX Series Ethernet Switches, Release 10.3
MSTP was originally defined in the IEEE 802.1s draft specification and later incorporated
into the IEEE 802.1Q-2003 specification.
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
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 [
To configure BPDU protection on a switch without a spanning tree, include the
statement at the [
edit ethernet-switching-options interface interface-name
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 statement has been included in the BPDU configuration, the
disable-timeout
interface automatically returns to service after the timer expires.
Use the operational mode command
edit protocols ( stp | mstp
clear ethernet-switching bpdu-error
Copyright © 2010, Juniper Networks, Inc.
| rstp )] hierarchy level.
bpdu-block
] hierarchy
.