Iot edge device went offline suddenly as on Apr 18 11:00 GMT+10

Hi Vishnu Priya,

Thanks for sharing the details.

If your IoT Edge devices went offline suddenly, it does not always mean there was an issue on the Azure side. In many cases, devices can show as offline due to connectivity or configuration issues on the device or network side.

Here are some simple checks you can try:

First, check IoT Hub connectivity Look at the connection logs or monitoring for your IoT Hub around the time when devices went offline. Try to see if all devices disconnected at the same time or only a few. This helps you understand if it is a network issue or something specific to devices.

Second, check device network and DNS Make sure your devices can reach the internet and Azure endpoints. Sometimes DNS issues or blocked outbound traffic can stop edgeAgent or edgeHub from connecting to IoT Hub.

Third, check network configuration like firewall and ports If you are using MQTT, make sure the required port is open on your network. Also check if any firewall or network rule was updated recently, which might block connections.

Fourth, check MTU or network path issues. in some environments like LTE or restricted networks, packet size mismatch can cause devices to drop connection. This can prevent the IoT Edge runtime from reaching IoT Hub.

Fifth, verify device status in IoT Hub Check that device identities are enabled in IoT Hub. Also confirm that no other process is connecting using the same device ID, as only one active connection is allowed.

Sixth, check storage and offline behavior IoT Edge devices can continue running even if they go offline, but they depend on local storage. If storage is full or message TTL is too low, it can impact behavior when connection is lost.

Also note that the Azure portal status may sometimes not reflect real connectivity. It is better to rely on logs and metrics to confirm whether the device is actually connected or not.

Here are some helpful references:

Monitor and troubleshoot IoT Hub connectivity https://learn.microsoft.com/azure/iot-hub/monitor-iot-hub

Understand IoT Edge offline capabilities https://learn.microsoft.com/en-us/azure/iot-edge/offline-capabilities

Troubleshoot IoT Edge issues https://learn.microsoft.com/azure/iot-edge/troubleshoot

If you can share whether all devices went offline or only specific ones, it will help narrow down the exact cause.

I Hope this helps. Do let me know if you have any further queries.

Thankyou!

Azure IoT Edge devices can continue operating offline for extended periods after an initial successful sync with IoT Hub. A sudden “offline” status in the portal does not always mean a platform-side outage; it can also be due to local connectivity, DNS, MTU, or storage/TTL limits on the edge device.

Use the following checks to diagnose and resolve:

1. Confirm IoT Hub health and connectivity monitoring
   • Use Azure Monitor and/or Event Grid on the IoT hub to inspect device connect/disconnect events around Apr 18 11:00 GMT+10 and see if all devices dropped at once or only specific ones. This helps distinguish a local network issue from a hub-level problem.
   • When monitoring via Event Hubs or logs, be aware that periodic disconnects can also be caused by SAS token renewal; filter out disconnects that are quickly followed by reconnects. Persistent disconnects indicate a real issue.
2. Check device-side connectivity and DNS
   • On each affected IoT Edge device, verify basic outbound connectivity to the internet and to Azure (for example, corporate networks may block public DNS or outbound ports).
   • If using Docker, ensure the container engine’s DNS configuration points to a DNS server reachable from the network. If a public DNS is blocked by the corporate network, configure Docker to use an internal DNS server via daemon.json and restart Docker, or set DNS per module in createOptions. Misconfigured DNS can cause edgeAgent/edgeHub to lose connection to IoT Hub.
3. Check MTU/network path issues (especially on LTE or constrained links)
   • For devices on LTE or similar networks, packet fragmentation due to MTU mismatch can prevent edgeAgent from reaching IoT Hub, leading to errors like “empty edge agent config” or “transient network error.”
   • Compare MTU on the host NIC and Docker network; if Docker’s MTU is higher than the physical adapter’s, recreate the Docker network (including azure-iot-edge) with an MTU that matches the adapter and restart the IoT Edge runtime.
4. Validate IoT Hub device status and protocol path
   • In the Azure portal, confirm that each device identity is Enabled in the IoT hub.
   • If devices use MQTT, ensure outbound port 8883 is open on firewalls and network security devices. IoT Hub supports only one active MQTT connection per device; if another process or instance connects with the same device ID, the existing connection is dropped.
5. Leverage IoT Edge offline capabilities and storage settings
   • IoT Edge devices and downstream devices can function offline indefinitely after an initial sync, but message storage is limited by TTL and disk space.
   • If devices are expected to be offline for long periods, increase storeAndForwardConfiguration.timeToLiveSecs in the $edgeHub desired properties and ensure sufficient disk space or host-mounted storage for the edgeHub module. This prevents premature message expiry while connectivity is being restored.
6. Interpret portal status correctly
   • When a device is offline, edgeAgent cannot update its reported properties, so the Azure portal may still show status 200 OK even though the device has no internet connectivity. Use connection logs and metrics rather than portal status alone to judge real connectivity.

If, after these checks, all network paths and configurations look correct and multiple, independent hubs/regions are affected at the same time, review Azure Service Health for any incident affecting IoT Hub in the region where the devices are registered and open a support case with the exact timeframe and hub name.

References:

• Monitor, diagnose, and troubleshoot Azure IoT Hub device connectivity
• Understand extended offline capabilities for IoT Edge devices, modules, and child devices
• Solutions to common issues for Azure IoT Edge