Juniper JUNOS OS 10.4 - FOR EX REV 1 Manual page 1899

Example: Configuring BPDU Protection on STP Interfaces to Prevent STP
Miscalculations on EX Series Switches
Requirements
Overview and Topology
Copyright © 2010, Juniper Networks, Inc.
EX Series switches provide Layer 2 loop prevention through Spanning Tree Protocol
(STP), Rapid Spanning Tree protocol (RSTP), and Multiple Spanning Tree Protocol
(MSTP). Configure BPDU protection on interfaces to prevent them from receiving BPDUs
that could result in STP misconfigurations, which could lead to network outages.
This example describes how to configure BPDU protection on access interfaces on an
EX Series switch in an RSTP topology:
Requirements on page 1795
Overview and Topology on page 1795
Configuration on page 1796
Verification on page 1797
This example uses the following hardware and software components:
Junos OS Release 9.1 or later for EX Series switches
Two EX Series switches in an RSTP topology
Before you configure the interfaces on Switch 2 for BPDU protection, be sure you have:
RSTP operating on the switches.
NOTE: By default, RSTP is enabled on all EX Series switches.
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, or MSTP topology, however, can lead to network outages by triggering an STP
misconfiguration. To prevent such outages, enable BPDU protection on those interfaces
that should not receive BPDUs.
Enable BPDU protection on switch interfaces connected to user devices or on interfaces
on which no BPDUs are expected, such as edge ports. If a BPDU is received on a
BPDU-protected interface, the interface is disabled and stops forwarding frames.
Two EX Series switches are displayed in Figure 46 on page 1796. In this example, Switch 1
and Switch 2 are configured for RSTP and create a loop-free topology. The interfaces
on Switch 2 are access ports.
This example shows you how to configure interface
edge ports and to configure BPDU protection. When BPDU protection is enabled, the
interfaces will transition to a blocking state when BPDUs are received on them.
Chapter 71: Examples of Spanning-Tree Protocols Configuration
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1795