I have 6 routers, one of them is the gateway to the internet for the other 5. So I have two /28 networks created between them. Each of the 5 remote routers uses two ethernet ports to get back to the gateway router via two seperate paths. The gateway router has one /28 network on each of the two ports. With the cost on all routers set to the default of 10 everything is load balanced perfectly for upload and download on all routers. On each remote router if I change the cost on one path to 9 the upload from that router to the gateway router all goes down that ethernet port, but the download remains balanced. Makes sense because the gateway router still has equal cost back to the remote router. So if I then change the cost on one of the gateway router ports to 9 than all the routers downloads go down that path only.

My question is how do I seperate these paths per router? For instance, I want one router to upload and download via one path only, but keep the other path for backup, and then another router use the opposite path?

Could you draw a quick diagram to explain in more detail? Are the routers all plugging into two separate switches on either interface?