Hi @CyberHome 

Thanks for reaching out to TP-Link Business Forums.

This is exactly how Link Backup feature should work.

When the Primary WAN is taking effect, the Backup WAN will be offline/disconnected. However, this does not really mean the Backup WAN is not working. The Omada Controller will still send some packets to ping some hostnames or IP addresses to detect if the Backup WAN is working or not.

If you want to keep both online/connected, you can simply disable Link Backup and just enable Load Balancing.

You may refer to this article: Common Questions About the Load Balancing, Link Backup(Failover) & Online Detection - Business Community

  @Gabriel-TP 

The issues is that the ER605 randomly disconnects the M7352 from the USB port and it is no longer accessible.

If the WAN1 link then fails, the failover does not work, as the USB device is no longer connected to the USB port and cannot be communicated with.

I also receive error notifications such as:

Hi @CyberHome 

This seems that the USB dongle is not working stably.

What's the model of it?

Can you set it as the primary WAN to check if the connection will last long?

Or if you have another one, could you swap it to have a try? Same issue?

You may change the Online Detection mechanism by navigate to Site View > Devices > ER605 > Manage Device > Config > Advanced > General > Echo Server to custom 8.8.8.8. This modification will allow the controller to detect if the WAN is online by pinging 8.8.8.8.

@Gabriel-TP 

The modem is a TP Link M7352 4G LTE Mobile Wifi device (https://www.tp-link.com/au/home-networking/all-mifi/m7352/). It is configured to NOT use "Power Saving" mode. and is on a separate LAN (192.168.0.0/24) rather than the main LAN address range (192.168.2.0/24).

The M7352 Web configuration interface is accessible, via it's 192.168.2 address from the main. LAN, when the device is shown as "Connected" but not when it randomly disconnects, and Omada Controller states that the device is down and disconnected.

I have already configured the Echo Server to be "Custom" with a value of 8.8.8.8

Unfortunately, I don't have another M7352 with which to test whether the issue still occurs.

As for testing the uptime of the USB Modem as the primary WAN, I will need to do this outside of normal business hours ( after 18:00 AEST), as it I do not want to impact normal business operations.

Hi @CyberHome 

In my opinion, this seems to be the MiFi device itself not works stably as the controller can still detect the primary WAN which is working with no issue. Also, you have set the Echo Server to 8.8.8.8 which helps identify if the WAN is online.

To identify if this is caused by the MiFi or the ER605, please help perform some tests when you are available:

1. Change the LET WAN DNS server to 8.8.8.8 / 8.8.4.4

2. Please refer to this article to connect the MiFi to your PC directly and confirm the connectivity pinging 8.8.8.8 -t : How to access Internet via USB cable with TP-Link Mobile Wi-Fi

3. Swap a different USB cable to connect the MiFi to the ER605; you may also switch the WAN port on the ER605.

4. Confirm if only LET WAN is actived will the connectivity lost.