What it probably ought to do is keep track of which gateway responds faster and then use the faster one, probably with some debounce logic in there. As you use one more, the response times for it get slower, as you're using up bandwidth with actual traffic. So it eventually switches over to the other apparently faster one, when it all starts again. Of course, that's pure speculation. I don't think that there's any way to really know what algorithm MS uses, and I'm too lazy to look to see how they do it in BSD, which is probably where MS stole it from to begin with anyway. You might be able to specify a metric, but that wouldn't do anything more than prefer one and end up using it all the time. It might notice when that gateway goes down, and switch over, if you're lucky.