Server 2008 Active Directory Sites Explained
From Active Directory perspective Site is well connected group of physical subnets which define internal replication boundary. Organizations usually create multiple Sites depending on their WAN infrastructure to control replication. It can also be use as a security scope to delegate authority to an administrator and used as an object to apply Group Policy. A Site contains Site name, Subnets that are associated to the Site, Site Links that are use to connect to other sites and DCs within the Site. Note: The term Intrasite replication refers to replication of DCs within the same site. The term Intersite replication refers to replication of DCs at different sites.
Relationship between Active Directory Sites and Domains
It is important to understand that Active Directory Sites and Domains can overlap. Active Directory Sites are independent to Active Directory Domains and vice versa. Multiple domains can exist within a single site as single domain can expand to multiple sites.
Server 2008 Active Directory Site Components
- Subnets
Subnets include list of well connected networks in the same site. I define “well connected” when speed is faster than 100/mbps. When a client—workstation looks for a Global Catalog, it prefers a Global Catalog in a same site / subnet as oppose to others. If subnets are not associated with a Site, clients can Global Catalog server in a different Site over WAN causing unnecessary traffic.
- Site Links
Site Links are the transport mechanism for Active Directory replication between sites. Site Links should be configured to mimic physical WAN connections between Sites. Replication interval and costs can be configured on Site Links. Active Directory Knowledge Consistency Checker (KCC) uses Site Links to build connections to make sure that replication occurs in efficient manner.
How to create a Site in Server 2008 Active Directory
- Open Active Directory Sites and Services console on a domain controller
- Right click the Sites container and chose New Site.
- Name the site choose a Site Link, lick Ok
- To create a subnet, right click the Subnets container, and choose New Subnet.
- Enter the network range, example: 192.168..1.0/24
- Choose the proper Site from the list to associate with the new subnet.
