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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.

Supported Platforms

Table 1 and Table 2 lists the platform series and line cards that support link degrade monitoring.

Table 1: MX Line Cards that Support Link Degrade Monitoring

Platform Series

MPC Line Cards Supported

DPC Line Cards Supported


  • MPC4E-3D-2CGE-8XGE


  • MPC-3D-16XGE-SFP

  • MPC3 with MIC3-3D-1X100GE-CFP

  • MPC3 with MIC3-3D-2X40GE-QSFPP

  • MPC3 with MIC-3D-2XGE-XFP

  • MPC3 with 2x10GE XFP MIC

  • MPC3 with 2x10GE XFP MIC

  • MPC5 with following variants:

    • 2CGE + 4XGE

    • 24XGE + 6XLGE

  • MPC6 with the following variants:

    • 2X100GE CFP2

    • 24X10GE SFPP

    • 24X10GE SFPP OTN

    • 4x100GE CXP


  • MPC7E-10G (non-MACsec mode)



    Note: Link degrade monitoring is not supported on MACsec-enabled MPC7E-10G and MIC-MACSEC-MRATE.

  • MPC10E-10C-MRATE (10G, 25G, 40G, 100G and 400G interfaces)

  • MPC10E-15C-MRATE (10G, 25G, 40G, 100G and 400G interfaces)

  • MX2K-MPC11E (10G, 40G, 100G, and 400G interfaces)








On 10-Gigabit Ethernet interfaces:

  • DPCE-R-Q-20GE-2XGE

  • DPCE-R-20GE-2XGE

  • DPCE-X-20GE-2XGE

Table 2: PTX Line Cards that Support Link Degrade Monitoring

Platform Series

Line Cards/PICs Supported

PTX3000 and PTX5000 (Junos)

  • P1-PTX-2-100GE-CFP

  • P2-100GE-CFP2


PTX10003 (Junos Evolved)

10G, 25G, 40G, 50G, 100G, 200G, and 400G interfaces

PTX10004 (Junos Evolved)

10G, 25G, 40G, 50G, 100G, 200G, and 400G interfaces

PTX10008 (Junos Evolved)

  • JNP10K-LC1201

  • PTX10K-LC1202-36MR (10G and 100G interfaces)