I am using RB750 to merge 4 DSL lines, but seem its not divining load to all 4 DSL lines.
following script. Where is the mistake ? could you please correct or add if need ...

Thanks



/interface set "ether1" name="ISP1"
/interface set "ether2" name="ISP2"
/interface set "ether3" name="ISP3"
/interface set "ether4" name="ISP4"
/interface set "ether5" name="LAN"

/ ip address
add address=192.168.20.1/24 network=192.168.20.0 broadcast=192.168.20.255 interface=LAN
add address=192.168.21.2/24 network=192.168.21.0 broadcast=192.168.21.255 interface=ISP1
add address=192.168.22.2/24 network=191.168.22.0 broadcast=192.168.22.255 interface=ISP2
add address=192.168.23.2/24 network=192.168.23.0 broadcast=192.168.23.255 interface=ISP3
add address=192.168.24.2/24 network=191.168.24.0 broadcast=192.168.24.255 interface=ISP4

/ ip firewall mangle
add chain=prerouting dst-address=192.168.21.2/24 action=accept in-interface=LAN
add chain=prerouting dst-address=192.168.22.2/24 action=accept in-interface=LAN
add chain=prerouting dst-address=192.168.23.2/24 action=accept in-interface=LAN
add chain=prerouting dst-address=192.168.24.2/24 action=accept in-interface=LAN

add chain=prerouting in-interface=ISP1 connection-mark=no-mark action=mark-connection \ new-connection-mark=ISP1_conn
add chain=prerouting in-interface=ISP2 connection-mark=no-mark action=mark-connection \ new-connection-mark=ISP2_conn
add chain=prerouting in-interface=ISP3 connection-mark=no-mark action=mark-connection \ new-connection-mark=ISP3_conn
add chain=prerouting in-interface=ISP4 connection-mark=no-mark action=mark-connection \ new-connection-mark=ISP4_conn

add chain=prerouting in-interface=LAN connection-mark=no-mark dst-address-type=!local \ per-connection-classifier=both-addresses:2/0 action=mark-connection new-connection-mark=ISP1_conn
add chain=prerouting in-interface=LAN connection-mark=no-mark dst-address-type=!local \ per-connection-classifier=both-addresses:2/1 action=mark-connection new-connection-mark=ISP2_conn
add chain=prerouting in-interface=LAN connection-mark=no-mark dst-address-type=!local \ per-connection-classifier=both-addresses:2/2 action=mark-connection new-connection-mark=ISP3_conn
add chain=prerouting in-interface=LAN connection-mark=no-mark dst-address-type=!local \ per-connection-classifier=both-addresses:2/3 action=mark-connection new-connection-mark=ISP4_conn

add chain=prerouting connection-mark=ISP1_conn in-interface=LAN action=mark-routing \ new-routing-mark=to_ISP1
add chain=prerouting connection-mark=ISP2_conn in-interface=LAN action=mark-routing \ new-routing-mark=to_ISP2
add chain=prerouting connection-mark=ISP3_conn in-interface=LAN action=mark-routing \ new-routing-mark=to_ISP3
add chain=prerouting connection-mark=ISP4_conn in-interface=LAN action=mark-routing \ new-routing-mark=to_ISP4

add chain=output connection-mark=ISP1_conn action=mark-routing new-routing-mark=to_ISP1
add chain=output connection-mark=ISP2_conn action=mark-routing new-routing-mark=to_ISP2
add chain=output connection-mark=ISP3_conn action=mark-routing new-routing-mark=to_ISP3
add chain=output connection-mark=ISP4_conn action=mark-routing new-routing-mark=to_ISP4

/ ip route
add dst-address=0.0.0.0/0 gateway=192.168.21.1 routing-mark=to_ISP1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.22.1 routing-mark=to_ISP2 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.23.1 routing-mark=to_ISP3 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.24.1 routing-mark=to_ISP3 check-gateway=ping

add dst-address=0.0.0.0/0 gateway=192.168.21.1 distance=1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.22.1 distance=2 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.23.1 distance=3 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.24.1 distance=4 check-gateway=ping

/ ip firewall nat
add chain=srcnat out-interface=ISP1 action=masquerade
add chain=srcnat out-interface=ISP2 action=masquerade
add chain=srcnat out-interface=ISP3 action=masquerade
add chain=srcnat out-interface=ISP3 action=masquerade