How to set up a backup LTE line on two Mikrotiks via VLAN?

Question

Mikrotik

There are two routers: 4011 (main) and 951 (the second one acts as a WiFi point, since 4011 does not have WiFi).
Two WiFi-networks are configured - the main one with access to local resources and the guest one purely with the Internet. Two VLANs were made according to the manual, everything is run by 4011 (DHCP, firewall, etc.), on 951 only access point settings.

Situation: the Internet on 4011 disappears, due to the lack of a USB port on 4011, I can connect the phone to 951 and distribute the Internet over the wire. From this, LTE1 appears in the interfaces, the client address given by the phone is dynamically pulled up.

By analogy, I made a third VLAN on the same trunk port in addition to the others, but I could not move further, the picture does not emerge in my head. Which of the ticks should organize the Internet, 951, 4011? How to combine in 951 the roles of both the slave wifa and the master wan?

Answer 1

Options.
1) Set up VRRP between Mikrotiks.
2) Set up a task for 4011, which will check the availability of the Internet and prescribe (turn on / off) the route to 951 when there is no Internet.