Load Balancing Outbound traffic between ISP Links with Big-IP LTM. HOW ?

So the general concept is that you have a forwarding virtual server ( this means it doesn't change the destination address or port ) and use a pool containing the routers for the different links. To start with, allow it to loadbalance over those links to see how it works and then try using different load balancing algorithms on the pool configuration. If you want to use your own loadbalancing scheme such as URL based then you can do that with LTM Traffic Policies or iRules but you will have to then change your virtual server setup.