v2-Dual-Ethernet_Load-Balancing-and-Failover.rsc

# Before detailed example overview, in a setup where we have private IP addresses behind the public IP, we should configure source NAT:
/ip firewall nat
add chain=srcnat action=masquerade out-interface=WAN1
add chain=srcnat action=masquerade out-interface=WAN2

# Let`s start with marking traffic with a firewall mangle rule, so we will have everything preconfigured when we go to the routing section:
/ip firewall mangle
add chain=output connection-state=new connection-mark=no-mark action=mark-connection new-connection-mark=GL-Inet out-interface=WAN1
add chain=output connection-mark=GL-Inet action=mark-routing new-routing-mark=to_GL-Inet out-interface=WAN1
add chain=output connection-state=new connection-mark=no-mark action=mark-connection new-connection-mark=Metal out-interface=WAN2
add chain=output connection-mark=Metal action=mark-routing new-routing-mark=to_Metal out-interface=WAN2

# We will split the routing configuration into three parts. First, we will configure Host1 and Host2 as a destination address in the routing section:
/ip route
add dst-address=208.67.222.222 scope=10 gateway=172.17.40.1
add dst-address=208.67.220.220 scope=10 gateway=172.18.40.1

# Now configure routes that will be resolved recursively, so they will only be active when they are reachable with ping:
/ip route
add distance=1 gateway=208.67.222.222 routing-mark=to_GL-Inet check-gateway=ping
add distance=2 gateway=208.67.220.220 routing-mark=to_GL-Inet check-gateway=ping

# Configure similar recursive routes for the second gateway:
/ip route
add distance=1 gateway=208.67.220.220 routing-mark=to_Metal check-gateway=ping
add distance=2 gateway=208.67.222.222 routing-mark=to_Metal check-gateway=ping

# Do not forget to add routes with routing marks:
/ip route
add distance=1 gateway=10.10.10.1 routing-mark=to_GL-Inet
add distance=2 gateway=10.20.20.2 routing-mark=to_GL-Inet
add distance=1 gateway=10.20.20.2 routing-mark=to_Metal
add distance=2 gateway=10.10.10.1 routing-mark=to_Metal