@Nikuda 

What do you mean dual WAN is not work?

Do you mean just one WAN is link up and the other WAN is link down?

Have you set any link backup rules??

Are you using it in standalone mode or Controller mode? If you power off the modem or disconnect the modem, the router can detect the WAN is offline immediately, but if you just unplug the DSL cable, Router think the modem is still active, it takes 1-2mins for Router to activate the link backup.

As you can see, on Controller mode, you can minimize the online detection interval to 1min.

Dear @Nikuda,

Nikuda wrote

Load Balancing doesn't work anymore.

Both WAN connections are linked, but it wont work.

To figure out the issue, please kindly elaborate on the problem with more detailed information.

What do you mean that both WAN connections are linked but it won't work?

How do you connect the ER7206 router? Are you using the ER7206 router in Controller mode or in Standalone mode?

For the two WAN connections, what's the WAN Status showing on the router (or controller) page?

Do you have WAN IP addresses (including default gateway ad DNS server) on the router (or controller) page?

If you unplug one link and keep a single WAN connected, can you get Internet access from the ER7206 router? 

If you connect directly to the ISP modem, bypass the ER7206, can you get Internet access immediately without further configuration? What IP addresses would you get from the ISP modem?

Thank you in advance for your great cooperation.

Dear @Emitplink,

Emitplink wrote

I configured properly the link backup on ER605 with primary VDSL and backup 4G connectivity.

The link backup is ok if I power off the main modem or remove the cable on primary WAN port, but it doesn't work if I remove the DSL cable on main router.

 

In this scenario is in standalone mode,

I waited for more then 5-6 minutes without result, I'm remain with primary WAN without connectivity.

What's the firmware version of your ER605 router?

If possible, please configure the 4G modem as the primary WAN and the VDSL modem as backup, remove the 4G card from the 4G modem, verify if the link backup would work as expected.

Dear @Emitplink,

Emitplink wrote

Thanks for your reply,

the fw is ER605(UN)_v1_1.0.1 Build 20210113.

Btw I noted that it works if I enable also the load balance plus Link Backup and Online detection. Do you confirm?

Load Balancing must be enabled so that the Link Backup function can take effect, and the Link Backup function works based on the results from Online Detection.

How to configure Link Backup on Dual WAN Router using the new GUI, https://www.tp-link.com/support/faq/2133/