Скачать или смотреть Free JNCIA Data Center - Broadcast Storm Control

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In this video, we look at broadcast storms and how to configure storm control on Juniper switches to prevent them from bringing down your network.

I demonstrate an actual broadcast storm in action so you can see exactly what happens when layer 2 loops cause ARP requests to continuously flood around the network.

A broadcast storm occurs when broadcast traffic continuously loops around a switched network, causing switches to constantly rewrite their MAC address tables and driving CPU usage through the roof. Unlike layer 3 which has TTL to prevent loops,

layer 2 has no native protection mechanism, so broadcast storms can literally grind your network to a halt.
Juniper switches have a default storm control profile that monitors BUM traffic - broadcast, unknown unicast, and multicast. By default, if traffic exceeds 80 percent of the interface bandwidth, the interface gets flagged as experiencing a storm.

I show you how to create a custom storm control profile under forwarding-options, setting your own bandwidth threshold (I use 50 percent in the demo) and configuring the action to automatically shutdown the interface when the threshold is exceeded.

Then we apply the storm control profile to specific interfaces using the family ethernet-switching storm-control command. You need to understand your network topology to know which interfaces need storm control - typically trunk ports rather than access ports.

I demonstrate how to verify storm control operation using show ethernet-switching interface, where you'll see the SCTL flag if an interface was shut down by storm control. You can also check the log messages for storm control violations.

Finally, I show you how to configure automatic recovery using the recovery-timeout option so interfaces automatically come back up after a specified time, or how to manually recover interfaces using the clear ethernet-switching recovery-timeout command.

Topics Covered:

Broadcast storm demonstration
How broadcast storms affect networks
BUM traffic (broadcast, unknown unicast, multicast)
ARP flooding and MAC table thrashing
Layer 2 vs layer 3 loop protection
Default storm control profile
Creating custom storm control profiles
Forwarding-options hierarchy
Bandwidth threshold configuration
Storm control actions (shutdown)
Applying profiles to interfaces
Storm control on trunk vs access ports
Verifying storm control operation
SCTL flag identification
Storm control logging
Automatic recovery timeout
Manual interface recovery
Clear ethernet-switching recovery-timeout

Commands Used:

set forwarding-options storm-control-profiles my-storm all bandwidth-percentage 50
set forwarding-options storm-control-profiles my-storm action shutdown
set interfaces xe-0/0/9 unit 0 family ethernet-switching storm-control my-storm
set interfaces xe-0/0/9 unit 0 family ethernet-switching recovery-timeout 100
show ethernet-switching interface xe-0/0/9
show log messages | match l2ald
clear ethernet-switching recovery-timeout

This is part of my complete free JNCIA Data Center series. New videos released every few days.