From a quick search i found this article on the Wiki...
https://wiki.mikrotik.com/wiki/ECMP_loa ... masquerade
According to this article:
You can use asymmetric bandwidth links also - for example one link is 2Mbps other 10Mbps. Just use this command to make load balancing 1:5
/ ip route
add dst-address=0.0.0.0/0 gateway=10.111.0.1,10.112.0.1,10.112.0.1,10.112.0.1,10.112.0.1,10.112.0.1 check-gateway=ping
However, if you read here:
https://wiki.mikrotik.com/wiki/Manual:I ... .29_routes
Is mentioned that:
Because results of the forwarding decision are cached, packets with the same source address, destination address, source interface, routing mark and ToS are sent to the same gateway. This means that ECMP route does not perform pure per-connection balancing, but it can be used to load balance connections if at least one of previously mentioned parameters is different than previous connection. See interface bonding if you need to achieve per-packet load balancing.