Return to index


Default Gateway basics


Any machine running an MS TCP/IP stack (and most other stacks) is automatically aware of all subnets to which it is directly attached. Therefore, it usually makes no sense to define one of a machines own IPs as its default gateway (there are special case exceptions to this).

The purpose of a default gateway, like all routers, is to route packets to remote (from the sending machine's point of view) subnets. So, if there is no router visible to a given machine or router, there is no reason to configure a default gateway on that machine.

The default gateway is the destination for any packets that don't have a specific route defined in the route table. As the name implies ('default' gateway), there can be only one active default gateway at a given time. If you have more than one gateway defined, the first one will always be used, unless it is unavailable. If this happens, the next gateway in the list will be tried.

Despite what MS's dialog boxes seem to imply, the default gateway is a system setting, not an adapter setting. That is, you can't have a different default gateway for each adapter. If you do configure a DG on more than one network adapter, the system will use only one of them (theoretically, the one assigned to the adapter that comes first in the binding order, but no guarantees). This may or may not be the correct one for your purposes.