I have a Windows Server machine that I have 2 nic's that are connected to 2 different isp's. Our DNS is hosted externally. What I am trying to do is set it up where when one isp goes down the 2nd isp will take over. I am pretty sure that round robin is not what i'm looking for as it would send people to the down isp 50% of the time. I have read about NLB, but everything I have seen relates to multiple computers in a cluster. I am not setting up a cluster. I have also thought about NIC teaming, but I do not know if that would work with our dsn being hosted externally. Any help would be greatly appreciated.
To achieve the goal you're after you have two options:
Option one is not something you want to roll your own (IMO) as it is complicated and hard to get right. If your hosting provider offers it as a managed service, I HIGHLY recommend you switch to using it.
For option two, there are a variety of devices available, I've used Ecessa PowerLink devices with good results. There are likely other devices which have similar features, but I have not used them.