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Managing Bandwidth Degradation

Certain errors result in packets being dropped by a system without notification. Other connected systems continue to forward traffic to the affected system, impacting network performance. A severely degraded fabric plane can be one of the reasons here.

By default, Juniper Networks routers attempt to start healing from such situations when the system detects issues with Packet Forwarding Engines. If the healing fails, the system turns off the interfaces, thereby preventing further escalations.

On Junos OS, you can use the configuration statement bandwidth-degradation at the [edit chassis fpc slot-numberfabric] hierarchy to detect and respond to fabric plane degradation in ways you deem fit. You can configure the router to specify which healing actions the router should take once such a condition is detected. You can also use the optional statement blackhole-action to determine how the line card responds to a 100 percent fabric degradation scenario. This command is optional and overrides the default fabric hardening procedures.

Note:

The bandwidth-degradation command and the offline-on-fabric-bandwidth-reduction statements are mutually exclusive. If both commands are configured, an error is issued during the commit check.

The bandwidth-degradation statement is configured with a percentage and an action. The percent-age value can range from 1 to 99, and it represents the percentage of fabric degradation needed to trigger a response from the line card. The action attribute determines the type of response the line card performs once fabric degradation reaches the configured percentage.

The statement is only configured with an action attribute, which triggers when the percentage of fabric degradation reaches 100 percent.

The following actions can be applied to either configuration statement:

  • log-only: A message gets logged in the chassisd and message files when the fabric degradation threshold is reached. No other actions are taken.

  • restart: The line card with a degraded fabric plane is restarted once the threshold is reached.

  • offline: The line card with a degraded fabric plane is taken offline once the threshold is reached. The line card requires manual intervention to be brought back online. This is the default action if no action attribute configured.

  • restart-then-offline: The line card with a degraded fabric plane is restarted once the threshold is reached, and if fabric plane degradation is detected again within 10 minutes, the line card is taken offline. The line card requires manual intervention to be brought back online.

Note:

This feature is available in the Junos OS Release 15.1R1.