Unblocking An Interface That Receives Bpdus In Error (Cli Procedure); Understanding Loop Protection For Stp, Rstp, Vstp, And Mstp On Ex Series Switches - Juniper EX9200 Features Manual

Unblocking an Interface That Receives BPDUs in Error (CLI Procedure)

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Understanding Loop Protection for STP, RSTP, VSTP, and MSTP on EX Series Switches

Copyright © 2017, Juniper Networks, Inc.
EX Series and QFX Series switches use bridge protocol data unit (BPDU) protection on
interfaces to prevent them from receiving BPDUs that could trigger a spanning-tree
misconfiguration. If BPDUs are received on a BPDU-protected interface, the interface
either shuts down or transitions to a blocking state and stops forwarding frames. In the
latter scenario, after the misconfiguration that triggered the BPDUs being sent to an
interface is fixed in the topology, the interface can be unblocked and returned to service.
To unblock an interface and return it to service using the CLI:
Automatically unblock an interface by configuring a timer that expires:
[edit protocol layer 2]
user@switch# set protocols layer2-control bpdu-block disable-timeout 30
All interfaces on the switch will be reenabled (unblocked) after the timer expires.
However, once an interface on the switch receives a new spanning-tree protocol BPDU,
the interface returns to the blocked state.
Manually unblock an interface using the operational mode command:
clear error bpdu interface
user@switch>
This command will only reenable an interface but the BPDU configuration for the
interface will continue to exist unless you remove the BPDU configuration explicitly.
Example: Configuring BPDU Protection on Edge Interfaces to Prevent STP
Miscalculations on page 219
Example: Configuring BPDU Protection on Interfaces to Prevent STP Miscalculations
on EX Series Switches on page 224
Understanding BPDU Protection for STP, RSTP, and MSTP on EX Series Switches on
page 217
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). Loop protection
increases the efficiency of STP, RSTP, and MSTP by preventing ports from moving into
a forwarding state that would result in a loop opening up in the network.
A loop-free network in spanning-tree topologies is supported through the exchange of
a special type of frame called bridge protocol data unit (BPDU). Peer STP applications
running on the switch interfaces use BPDUs to communicate. Ultimately, the exchange
of BPDUs determines which interfaces block traffic (preventing loops) and which
interfaces become root ports and forward traffic.
Chapter 10: Using BPDU Protection, Root Protection, and Loop Protection
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