We want to set up a site-to-site VPN between routers in our two branch offices and our corporate headquarters. We have a T1 at our headquarters and ADSL at the branches. We are running Windows Small Business Server at the main office. Ideally, workstations in the branches would login directly to our SBS server to the same domain that workstations in the main office do.
Do I need to have all offices on one big subnet, or should I separate them into three separate subnets? I guess I am confused about how the domain is resolved when logging in on a Windows Network. If it uses DNS to resolve it then I suppose its fine on seprate subnets, but I'm not sure how that works.
We are a small company of about 20 employees.