i have routerboard 450G
Have 3 dhcp from the same ISP
gateway for all wan's is 12.10.2.100 and dns 12.10.2.100

but won't work it right.
all traffic goes from wan3 not balanced.(((
help to fix problem

/ ip address
add address=192.168.88.1/24 network=192.168.0.0 broadcast=192.168.0.255 interface=Local
dhcp-client add interface=wan1 user-peer=yes add-default-route=yes disable=no
dhcp-client add interface=wan2 user-peer=yes add-default-route=yes disable=no
dhcp-client add interface=wan3 user-peer=yes add-default-route=yes disable=no

/ ip route
add dst-address=0.0.0.0/0 gateway=12.10.2.100%wan1,12.10.2.100%wan2,12.10.2.100%wan3 check-gateway=ping

/ ip firewall nat
add chain=srcnat out-interface=wan1 action=masquerade
add chain=srcnat out-interface=wan2 action=masquerade
add chain=srcnat out-interface=wan3 action=masquerade

/ 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=input in-interface=wan3 action=mark-connection new-connection-mark=wan3_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=output connection-mark=wan3_conn action=mark-routing new-routing-mark=to_wan3

/ ip route
add dst-address=0.0.0.0/0 gateway=12.10.2.100%wan1 routing-mark=to_wan1
add dst-address=0.0.0.0/0 gateway=12.10.2.100%wan2 routing-mark=to_wan2
add dst-address=0.0.0.0/0 gateway=12.10.2.100%wan3 routing-mark=to_wan3

The traffic is going via one interface, which dynamic /ip route to gateway is in active state (A letter is added to route).
There is no interface routing possible for DHCP, it is available for PPP interfaces.

check this: http://forum.mikrotik.com/viewtopic.php ... 13#p192513