I can use two routers in my home.
Router A is from my ISP. I can deactivate the DHCP server on it and the gateway ip address is configured to 192.168.0.1.
Router B is behind an ethernet port in my flat. It's provided by my property management. I have no access to it, a DHCP server is running on it. It's gateway address is configured to 192.168.0.254. Currently an openwrt device configured as dump ap is directly connected to it.
Is it possible to install a redundancy setup here? Normally i want to route everything over router A, but if this fails i want to switch to router B.
My idea was to let the openwrt device function as the DHCP server in the network. On router A i can deactivate the DHCP server. DHCP requests should never reach router B, as the only connection to it is going over the openwrt device. Perhaps i have to setup a firewall rule to it, but that part seems to be solvable to me.
But i have problems with the second part. Detecting that router A fails and then switch all devices in the network to router B. Is there a way to do this? Is this even the correct way to do this?