Chapter 11. Site Topology


Active Directory needs information about the underlying network to determine how domain controllers should replicate and what domain controller(s) are optimal for a given client to authenticate with. This network information is often referred to as the site or replication topology, and it consists of numerous object types that represent various aspects of the network.

At a high level, a site is a logical collection of high-speed LAN segments. One or more subnets can be associated with a site, and this mapping is used to determine which site a client belongs to, based on its IP address. Sites are connected via site links, which are analogous to WAN connections. Finally, each domain controller in a site has one or more connection objects, which define a replication connection to other domain controllers.

These site topology objects are contained under the Sites container within the Configuration naming context. Figure 11-1 shows an example of the site topology hierarchy using the Active Directory Sites and Services snap-in.

Directly under the Sites container are the individual site containers, plus containers that store the site link objects (cn=Inter-site Transports) and subnets (cn=Subnets). Three objects are included within a site:

  • An NTDS Site Settings (nTDSSiteSettings) object that contains attributes that can customize replication behavior for the whole site

  • A License Site Settings (licensingSiteSettings) object that can be used to direct hosts ...

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