As you know, a site is an IP subnet, or two or more subnets that are connected by a high bandwidth link. Sites are used to control network traffic related to logon authentication and Active Directory replication.
As an administrator, you may need to create multiple sites if your network is large and geographically dispersed. Creating sites isn't something that is done frequently, or at all with smaller networks. With a large network, sites are created when you initially set up the Win2000 network. If you added a new branch office in a new location you might create more sites.
How to create a site
Creating a site involves providing a name for the new site and associating the site with a site link. You must either log on as a member of the Enterprise Admins group to create sites or use the Secondary Logon Service to start Active Directory Sites and Services in the security context of a member of the Enterprise Admins group. Once in Sites and Services, you must complete these steps:
Open Active Directory Sites and Services from the Administrative Tools menu.
In the console tree of Active Directory Sites and Services, right-click Sites, and then click New Site.
In the Create New Object - (Site) dialog box, type a site name in the Name box.
Click a site link, and then click OK. (Select the default site link if it is the only link available.)