(If you need to understand how Load Balance works, please read this first: Common Questions About the Load Balancing, Link Backup(Failover) & Online Detection)

 

This Article Applies to:

 

All routers with Load Balance function.

 

Application Scenario:

 

 

Issue Description:

 

Not able to switch to the backup WAN when the primary WAN fails.  Online Detection cannot precisely detect the failure.

WAN shows incorrect status or primary WAN is not able to be prioritized.

 

Troubleshooting:

 

1. Make sure you have enabled the Load Balancing.

 

Load Balancing is enabled by default. To use the Link Backup for failover, you must enable the Load Balancing. Disabling it will make all related features ineffective. (Link Backup is a feature that belongs to the Load Balancing.)

 

We recommend you use the parameters below. In Controller mode, you don't have to enable Application Optimized Routing.

 

 

2. Choose the desired mode for Link Backup.

 

There are two backup modes. Please choose according to your expectations.
Link Backup: The system will switch all the new sessions from one dropped line automatically to another to keep an always on-link network.

Always Link Primary: Traffic is always forwarded through the primary WAN port unless it fails. The system will try to forward the traffic via the backup WAN port when it fails, and switch back when it recovers.
 

3. Make sure your Online Detection is proper.

 

By default, we have URLs used for the online connectivity test. However, you can manually set it. But this has to be set correctly. Or your Online Detection may not work properly. When it is set to Manual mode, your IP specified here must be correct and available. If you set it to Always Online, then this WAN is never considered offline regardless of its real connectivity.

 

In standalone:

 

 

In Controller, the Online Detection is named differently. It's called Echo Server.

 

 

Note:

 

1. When you enable Link Backup, the backup WAN will be displayed as Offline. This is normal behavior. Traffic will not flow through the backup WAN until it is switched on when the primary WAN fails. 

2. Link Up is the status of the physical connection of the WAN port. If the router detects a cable plugged in, then it'll display Link Up. This does not mean Internet is online or offline.

3. We cannot make a zero-feeling (insensible) failover when switching to the other WAN when the network fails. Due to the differences in TCP and UDP, we cannot make it happen. Sometimes, you have to reset the session by refreshing the page.

4. If you are in standalone, you cannot set the Online Detection period, unlike the Controller mode. In this case, you may face a few seconds downtime before it detects the offline and switch over. We have optimized in previous firmware updates and this is acceptable in our opinion. 

5. The router is fully capable of prioritizing the primary WAN after a reconnection. If you have any questions about this, please follow the instructions at https://community.tp-link.com/en/business/forum/topic/621018?replyId=1251914

If you have trouble with this, please Start a New Thread and paste your results with the same test methods.

 

Update Log:

 

Feb 20th, 2024:

Update the format.

 

Jan 10th, 2024:

Add KB article to Recommended Threads.

Add KB article for extra reference in understanding the Load Balance.

 

Recommended Threads:

 

Troubleshooting "Unsupported Browser" or "Incorrect Password" After the Firmware Upgrade on Business Routers

Troubleshooting Custom DDNS Is Not Working

Common Questions About the Load Balancing, Link Backup(Failover) & Online Detection

 

Feedback:

 

• If this was helpful, welcome to give us Kudos by clicking the upward triangle below.
• If there is anything unclear in this solution post, please feel free to comment below.
• If you encounter such an issue, please follow the troubleshooting above to check your settings. Besides, ensure your Omada Controller and Gateway are running with the latest firmware.
• If the issue still exists after you try the suggestion above, please feel free to comment below or contact our support team with a detailed description of your issue and the steps you have tried.

 

Thank you in advance for your valuable feedback!

 

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