If you have multiple network adapters in your computer and you configure a default gateway for each adapter (which creates a default route in the IP routing table for all destinations that are not located on the subnet), information on your network might not be routed to the correct destinations if you connect to disjoint networks—separate networks that are not designed to communicate directly.

Only a single gateway is used for all destinations that are not located on the subnet, even when you configure multiple default gateways. An example of this is when a computer is connected to both an intranet with multiple subnets and the Internet. With a default gateway configured for both adapters, you can either communicate with all computers on the Internet or all computers on the intranet, but not both.

To solve this problem, do the following:
  • Configure a default gateway for the network adapter that's connected to the network with the most routes (usually the network adapter that's connected to the Internet).
  • Don't configure a default gateway for any other network adapter. Instead, use static routes or dynamic routing protocols to add the routes for the other disjoint networks to the local IP routing table. If the routing infrastructure uses Routing Information Protocol (RIP) for IPv4, you can turn on RIP Listener in Windows, which allows your computer to learn other routes on the network by "listening" to broadcast RIP messages, and then adding IPv4 routes to the routing table. If the routing infrastructure doesn't use RIP, you can't use RIP listening.


Read full tutorial here.