I have a TP-Link XC220-G3v XPON router as my main router on which there are devices attached, two of them are my NAS and my MR600 router (which I'm using if I am to lose my main internet, its running on Wireless Router Mode with 3G/4G backup enabled, main reason is that I have WiFi cameras attached to it)

Now I want to add my camera to my NAS but the two are on different subnet.

I can't disable DHCP because then I cannot access my router.

My Main router is on Subnet 192.168.1.0/24

Where as my backup router is on Subnet 192.168.0.0/24

I had ONLY studied networking in College but now I don't remember most of the things so.

@Sunshine can you help me out?

I tried creating a static route after watching this video

But I am still unable to access the subnet.