---
title: High availability
slug: edgemanager/lem-user-guide/manage-edge-devices/edge-devices/edge-device-details/high-availability
docTags: 
createdAt: 2026-06-03T20:07:28.927Z
---

High Availability (HA) keeps Litmus Edge running when a device goes down or is taken offline. It works by pairing a primary (active) node with a backup (standby) node that stays in sync and takes over automatically if the primary fails. 

:::hint{type="warning"}
**Note:** High Availability is currently available as a beta feature.
:::

:::hint{type="info"}
**Note:** High Availability management requires Litmus Edge Manager (LEM) 2.34.0 or later and Litmus Edge 4.0.5 or later on both devices in the pair.
:::

## How LEM monitors high availability pairs

Litmus Edge Manager (LEM) polls each HA pair periodically to retrieve the current status and role of each node. When LEM detects a failover, it automatically updates device roles in the UI. You do not need to manually update roles after a promotion.

LEM reports three pair status values:

- **Healthy**: Both nodes are reachable and the pair is operating normally
- **Degraded**: One node is unreachable or the pair is not fully synchronized
- **Unknown**: LEM cannot determine pair status, typically because polling has not completed or a node is offline

## Heartbeat monitoring

HA performs heartbeat checks at 2-second intervals. Failover is triggered after three consecutive missed heartbeats. The following fields display on the primary node:

| **Field**                | **Description**                                    |
| ------------------------ | -------------------------------------------------- |
| **Last Sent**            | Last heartbeat sent to the backup node             |
| **Last Received**        | Last heartbeat received from the backup node       |
| **Consecutive Failures** | Number of consecutive missed heartbeats            |
| **Peer Reachable**       | Whether the backup is reachable from the primary   |
| **Interval**             | Frequency of heartbeat signals in seconds          |
| **Failure Threshold**    | Number of missed heartbeats that triggers failover |

## Configuring high availability: LEM vs. Litmus Edge

HA pairs can be configured two ways. Both require a primary and a backup device.

- **From LEM:** Configure the pair centrally without logging into each device. Recommended when both devices are already connected to LEM and you want to manage HA from a single interface.
- **From each Litmus Edge instance directly:** Log into each device and configure the pair at the device level. Useful when devices are not yet connected to LEM or are in an air-gapped environment. See [High Availability (Litmus Edge)](docId:6VCpUpiHFFAMQCgjeWeU6) in the Litmus Edge documentation.

## Configure a high availability pair

This section provides an overview of HA configuration. For full step-by-step instructions, see [Setup a High Availability edge device pairing](docId\:oKxpTsi0_vVfXqog13hQS).

To configure an HA pair:

1. In LEM, navigate to **Edge Devices**, click a device ID, and select the **High Availability** tab.
2. Toggle **Enable High Availability** on.

   ::Image[]{src="https://api.archbee.com/api/optimize/SSUUxKZUk9bFTEPNn_6Zo/NEWXeIAbiTjXM2jj1COC0_image.png" size="80" width="1567" height="712" darkWidth="1567" darkHeight="712" position="flex-start" showCaption="false"}
3. In the *Configure High Availability* dialog, select a role, select a peer device, confirm IP addresses, and review the configuration.
4. Click **Create Configuration**.
5. Click **Enable**.

High Availability becomes enabled between the primary and backup nodes.