Following up on another question I asked eariler. Here is the response I received for an expert:
If you have no subnets, then you have only one site....presumably the default first site. AD does not know that your have two sites, and so the PCs in one site may be using the DCs in another site. If you have a fast connection between the two sites, it won't matter very much, but you really should define the subnets for each location, define two different sites, and move the DCs to the appropriate sites.
My question is "How do I configure the subnet for two locations?".