https://aacable.wordpress.com/2011/07/27/mikrotik-dual-wan-load-balancing-using-pcc-method-complete-script-by-zaib/

  * /ip address
  * add address=192.168.0.1/24 network=192.168.0.0 broadcast=192.168.0.255 interface=Local
  * add address=192.168.1.2/24 network=192.168.1.0 broadcast=192.168.1.255 interface=WAN1
  * add address=192.168.2.2/24 network=192.168.2.0 broadcast=192.168.2.255 interface=WAN2
  * /ip dns set allow-remote-requests=yes cache-max-ttl=1w cache-size=5000KiB max-udp-packet-size=512 servers=8.8.8.8
  * /ip firewall mangle
  * add chain=input in-interface=WAN1 action=mark-connection new-connection-mark=WAN1_conn
  * add chain=input in-interface=WAN2 action=mark-connection new-connection-mark=WAN2_conn
  * add chain=output connection-mark=WAN1_conn action=mark-routing new-routing-mark=to_WAN1
  * add chain=output connection-mark=WAN2_conn action=mark-routing new-routing-mark=to_WAN2
  * add chain=prerouting dst-address=192.168.1.0/24 action=accept in-interface=Local
  * add chain=prerouting dst-address=192.168.2.0/24 action=accept in-interface=Local
  * add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=both-addresses-and-ports:2/0 action=mark-connection new-connection-mark=WAN1_conn passthrough=yes
  * add chain=prerouting dst-address-type=!local in-interface=Local per-connection-classifier=both-addresses-and-ports:2/1 action=mark-connection new-connection-mark=WAN2_conn passthrough=yes
  * add chain=prerouting connection-mark=WAN1_conn in-interface=Local action=mark-routing new-routing-mark=to_WAN1
  * add chain=prerouting connection-mark=WAN2_conn in-interface=Local action=mark-routing new-routing-mark=to_WAN2
  * /ip route
  * add dst-address=0.0.0.0/0 gateway=192.168.1.1 routing-mark=to_WAN1 check-gateway=ping
  * add dst-address=0.0.0.0/0 gateway=192.168.2.1 routing-mark=to_WAN2 check-gateway=ping
  * add dst-address=0.0.0.0/0 gateway=192.168.1.1 distance=1 check-gateway=ping
  * add dst-address=0.0.0.0/0 gateway=192.168.2.1 distance=2 check-gateway=ping
  * /ip firewall nat
  * add chain=srcnat out-interface=WAN1 action=masquerade
  * add chain=srcnat out-interface=WAN2 action=masquerade