Dual WAN DNS issue on

[Asmer]

I have a problem with Dual WAN on my RT-AX58U.
I've read about little chances on having some support related to Dual WAN, but the problem here is that the same configuration is working on stock firmware.

My primary WAN is a simple DHCP from ISP. As a secondary WAN, I use an ethernet cable connected to 4G router using LAN1 port.
Everything woks fine when both primary and secondary ISP's are alive. But when primary ISP is ok, and secondary goes down - my internet drops.

After some testing I found out that the problem is with DNS requests - they always go through secondary WAN. So if secondary WAN goes down, DNS stops working, even when primary WAN works well for direct ICMP echoes.

I think this is also related to the fact that I have DNS over TLS configured.
Again, the same case works well on stock. Is it possible to have some advice on that?

Thanks a lot in advance!

 

[L&LD]

Welcome to the forums @Asmer.

How have you configured RMerlin's firmware? After flashing it, did you do a full reset to factory defaults, without importing any old backup config files?

What differences in setup do you implement between stock and RMerlin firmware?

A few screenshots would help here, I believe, to know how you're setting up the router.

 

[Ranger802004]

I have a problem with Dual WAN on my RT-AX58U.
I've read about little chances on having some support related to Dual WAN, but the problem here is that the same configuration is working on stock firmware.

My primary WAN is a simple DHCP from ISP. As a secondary WAN, I use an ethernet cable connected to 4G router using LAN1 port.
Everything woks fine when both primary and secondary ISP's are alive. But when primary ISP is ok, and secondary goes down - my internet drops.

After some testing I found out that the problem is with DNS requests - they always go through secondary WAN. So if secondary WAN goes down, DNS stops working, even when primary WAN works well for direct ICMP echoes.

I think this is also related to the fact that I have DNS over TLS configured.
Again, the same case works well on stock. Is it possible to have some advice on that?

Thanks a lot in advance!

Use my WAN Failover script in my signature, it switches the DNS plus many other things during failover.

 

[Asmer]

Hello! Sorry for being silent for a long time.

I finally got a chance to dig the problem carefully and found the problem.

My secondary WAN was sending IP addresses for DNS servers over DHCP that were configured in DNS over TLS section of the router.
That led to requests to those IP addresses to be always routed to Secondary WAN, even if it's down.

Altering the DNS servers on the secondary WAN side fixed the issue