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show loop-detect enhanced interface

date_range 28-Feb-25

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Syntax

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show loop-detect enhanced interface
<interface-name>

Description

Display status information about leaf device logical interfaces with loop detection enabled in a Layer 2 network.

You can configure loop detection on leaf devices for server-facing Layer 2 logical interfaces, and specify an action that the leaf device performs on the interface when it detects a loop, such as bringing the interface down. You can also configure an interval after which the device will automatically revert the interface to its state prior to the loop detection action following repair of the loop condition.

After you’ve enabled loop detection, the interfaces periodically send multicast loop-detection protocol data units (PDUs). If the interface receives a loop-detection PDU, which indicates a loop exists, the interface triggers the configured action to break the loop. The network administrator might then need to repair the conditions that caused the loop before reverting the interface to its state prior to loop detection. This command shows the configured loop detection parameters, current interface status, and detail about the remote interface that formed the loop.

Beginning with Junos 24.4 we’ve added support for monitoring all VLANs on a logical interface with the vlan-id all configuration option at the [edit protocols loop-detect enhanced interface] hierarchy level. The Lightweight Loop Detection with Scale feature detects network loops across multiple VLANs and interfaces, improving network stability and performance.

When you configure the loop-detect vlan-id all option, the show loop-detect enhanced interface command:

Displays all in the Vlan-id output field.
Displays Vlan and Loop on other vlans as additional loop detection fields under the Current status field.

Options

interface-name

Display loop detection status for the specified logical interface.

If you don't specify an interface name, this command displays loop detection status for all logical interfaces that have this feature enabled.

Required Privilege Level

view

Output Fields

Table 1: show loop-detect enhanced interface Output Fields
Field Name	Field Description
Interface	Local interface name with loop detection configured.
Vlan-id	`vlan-id`—Local interface VLAN ID for which loop detection is configured. all—All VLAN IDs on the local interface.
ESI	Ethernet Segment ID (ESI) associated with the local interface.
Current status	Current status of the interface—Loop-detected or Normal [Link Up] (no loop detected) This output section displays the following additional fields if the interface detected a loop. These fields describe the interface that routed loop detection PDUs back to the local interface: Remote Host: Remote host name. Remote Chassis: Remote host chassis ID. Remote Interface: Remote interface name that is looping PDUs. Remote ESI: ESI associated with the remote interface. Configuring Scaled Loop Detection using the loop-detect vlan-id all option adds the following fields. Vlan: Local interface VLAN ID where loop is first detected. Loop on other vlans: Other vlans on this local interface for which loop is detected. Detailed peer information for these other vlans will not be displayed. Note: The interface causing the loop might be on the same local device or on a remote device.
Last loop-detect time	Timestamp when the device initially detected the loop and changed the interface status to Loop-detected. When the interface has no `Revert Interval` set, or the `Revert Interval` timer is counting down the revert time after a loop has been cleared, if the feature detects a new loop, it updates the `Last loop-detect time` output field to display that most recent time loop detection time.
Receive statistics	Number of loop-detection PDUs received since the current loop detection period timestamp.
Action configured	The configured action that the device triggers upon loop detection.
Action count	Cumulative count of loop detection actions triggered on the local interface.
Transmit Interval	Default or configured interval at which the interface sends loop detection PDUs.
Revert Interval	Configured interval after the loop condition is repaired in which the interface state reverts to the previous state before the loop detection action occurred.

Sample Output

show loop-detect enhanced interface interface-name (no loop detected)
show loop-detect enhanced interface interface-name (loop detected)
show loop-detect enhanced interface (EX4300-48MP, all interfaces configured with loop detection)
show loop-detect enhanced interface (ACX7100-32C, ACX7100-48L, all interfaces configured with loop detection, no loop detected)
show loop-detect enhanced interface (ACX7100-32C, ACX7100-48L, all interfaces configured with loop detection, loop detected)
show loop-detect enhanced interface interface-name (Lightweight Loop Detection with Scale [loop-detect vlan-id all] configured, no loop detected)
show loop-detect enhanced interface interface-name (Lightweight Loop Detection with Scale [loop-detect vlan-id all] configured, loop detected)