Question about defining multiple default gateways

Hi,

Have a network at a colo facility where I was given 5 different Clas C subnets, 2 on one network and 3 on a second network.

My Mikrotik has 2 NICs, one going to each ISP

provider A = nets 110.x.x.x, 82.x.x.x
provider B = nets 111.x.x.x, 113.x.x.x, 121.x.x.x

Any traffic from 113. network has to go out interface B
Any traffic from 82. network has to go out interface A
etc

How do I set up default gateway settings to ensure the packets are leaving out the right interface, depending on which subnet its coming from?

Thanks!

Routing marks.

A google of “mikrotik routing marks” brought me to a page which I think describes what I’m trying to do:

http://wiki.mikrotik.com/wiki/Load_Balancing_over_Multiple_Gateways

Thanks!