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Link Degrade Monitoring Overview

Link degrade monitoring enables you to monitor the quality of physical links on Ethernet interfaces and take corrective action when the link quality degrades beyond a certain level. You can configure this feature by applying the link-degrade-monitor statement at the [edit interfaces interface-name] hierarchy level.


Ethernet links (using Link Fault Signaling (LFS) protocol), Layer 2 and Layer 3 protocols support physical link monitoring. However, these existing mechanisms cannot detect BER ranges that are very low (for example, 10-13 through 10-5).

When you configure link degrade monitoring on your device, this feature continuously monitors bit error rate (BER) value of the link and initiates a corrective action (media-based) when the BER value breaches a user-configured threshold. You can configure the threshold by using the thresholds statement at the [edit interfaces interface-name link-degrade-monitor] hierarchy level. The feature can detect a BER value as low as 10-13 through 10-5, helping you prevent or minimize packet drops in physical links.

You can configure autorecovery or manual recovery method for the degraded link. In the case of manual recovery, you need to use the request interface link-degrade-recover interface-name statement to recover the degraded link. If autorecovery is configured, automatic recovery of the degraded link is attempted at the user configured intervals, and when the link’s BER value is within the configured limit, the link is recovered.

When you configure link monitoring (by using the link-degrade-monitor statement), you can set the following options:

  • BER threshold value at which the corrective action must be triggered on an interface. Use the thresholds (set | clear) statement to configure the BER threshold value or clear the BER threshold value.

  • Link degrade interval value, which determines the number of consecutive link degradation events that are considered before any corrective action is taken. Use the thresholds interval intervalvalue statement to configure the interval.

  • Warning threshold value for link degradation. Use the thresholds warning (set | clear) statement to configure the warning threshold value or clear the warning threshold value.

  • Action that is taken when the configured BER threshold level is reached. Use the thresholds actions media-based statement to configure the action to be taken.

  • Automatic or manual recovery. Use the recovery (auto | manual) statement to configure recovery.

  • Time interval after which automatic recovery of the degraded link must be triggered. Use the recovery timer timer-value statement to configure the time interval.