RouterOS

/ip route
add dst-address=8.8.8.8/32 gateway=10.0.1.1 scope=10 comment="Primary Route to DNS"
add gateway=8.8.8.8  distance=1 check-gateway=ping   comment="Primary Route Check"
add gateway=10.0.2.1 distance=2                      comment="Secondary"

• http://www.prinmath.com/ham/mikrotik-failover.htm
• http://oriolrius.cat/blog/2016/08/29/internet-fail-over-connection-with-mikrotik/
• https://wiki.mikrotik.com/wiki/Advanced_Routing_Failover_without_Scripting