Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


loop-detect (EVPN)


Hierarchy Level


Configure lightweight loop detection on server-facing Layer 2 (L2) interfaces of the leaf devices in an EVPN-VXLAN fabric. This feature can detect the following types of Ethernet loops:

  • A loop between two interfaces in different Ethernet segments (ESs). This loop is typically caused by miswiring fabric components.

  • A loop between two interfaces with the same Ethernet segment identifier (ESI). This loop is typically caused by miswiring a third-party switch to the fabric.

We recommend that you enable loop detection initially before you configure EVPN, so you can detect any loops and take corrective actions before EVPN traffic is flowing through the network. Otherwise, if you bring up an EVPN fabric with loops, even with this feature enabled, traffic can continue to flow through the loops for some time while the network stabilizes.

After you’ve enabled loop detection, the interfaces periodically send multicast loop-detection protocol data units (PDUs). If a loop detection-enabled interface receives a PDU, it detects a loop and triggers the configured action to break the loop. For example, if you configured the interface-down action, the device brings the interface down. After you have repaired the loop condition and the revert-interval timer expires, the device reverts the loop-detection action and brings the interface up again.

Use the following command to manually revert (clear) the status on one or all interfaces where the device detected a loop:

If you don't specify an interface name, the clear loop-detect enhanced command reverts the interface status for all interfaces where the device performed a loop detection action. You can use the clear command in the following cases:

  • When you didn't configure a revert-interval value. In that case, the interface loop detection status doesn't clear until you clear it manually.

  • If you configured a revert-interval, but you want to revert the status before the interval expires.

Use the following command to see loop detection status information for an interface or all interfaces with loop detection enabled:


interface (name | all)

Specify the name of a server-facing L2 interface on which you want to enable lightweight loop detection, or enable this feature on all such interfaces.


If the feature detects a loop, you can configure either of the following actions:

  • Values:

    • interface-down—The device brings down the interface on which the loop was detected.

    • laser-off—The device turns off the optics transmit laser.


      Platforms that support the laser-off port capability support this action.


(Optional) Specify the interval, in seconds, in which the interface will revert to its previous state after the loop condition is fixed. For example, if the loop-detect-action is interface-down, after the loop condition is repaired and the interval expires, the device brings the interface up again.

  • Default: 0


    If you retain this default setting (0) and a loop detection event triggers the interface-down action, you must enter the clear loop-detect enhanced interface <interface-name> command to bring the interface back up. Until you enter the clear command, the interface remains down.

  • Range: 0 through 300 seconds


(Optional) The interval in seconds or minutes at which the interface transmits loop detection PDUs.

  • Default: 1 second (1s)

  • Values:

    • 10 minutes (10m)

    • 1 minute (1m)

    • 10 seconds (10s)

    • 1 second (1s)

vlan-id vlan-id

(Required for trunk interfaces, enterprise style interface configurations or service provider style configurations) Specify the VLAN identifier for the interface.

  • Range: 1 through 4094

Required Privilege Level


Release Information

Statement introduced in Junos OS Release 20.4R1.

Statement support added to ACX-Series (ACX7100-32C, ACX7100-48L) devices in Junos OS Evolved Release 22.4R1.