What
routing protocols are you running on that Linux box?
The traditional (and still correct) approach is to run BGP on your exterior router for load balancing between the two ISP's. However, this does require cooperation with both ISP's.
You
could rig something up manually, by setting up
static routes to some networks through the second ISP. That would be simple, but would require you to guesstimate load "balancing" -- and it would not provide redundancy in case one of your ISP's failed.
It would be really odd, but theoretically you could also use
IPVS to implement load balancing. IPVS is designed to load balance
incoming traffic, but I can't see why it could not be pressed into service to balance outgoing traffic also. That might be pushing the technical envelope.
Linear Mode
