Site Creation and Configuration in Active Directory

Site Creation and Configuration in Active Directory

The job of configuring and creating sites belongs to the administrators who manage Active Directory, but those who manage the network must be well informed and possibly involved in the design. Whether Active Directory and the network are handled by the same or different groups, they affect each other, and undesired network utilization or failed network connectivity might result. For example, if the Active Directory administrator defines the entire enterprise as a single site, and several Active Directory changes happen each day, replication connections would exist across the enterprise, and replication traffic might be heavy, causing poor network performance for other networking services. On the other side, if the network administrator allows only specific ports to communicate between certain subnets, adding Active Directory might require that additional ports be opened or involve specific network requirements on the servers at each location.

For these examples, the company locations and IP addresses in Table 1 will be used. The company has a hub-and-spoke topology, with each branch office connected to the main office. The main office has an IPv4 and an IPv6 subnet.

Table 1. Common Subnet Mask to Prefix Length
Location	Role	Subnets	WAN Link
India	Main Office	192.168.3.0/24 2001:db8:1234:5678::/64
India	Branch Office	192.168.10.0/24	T3
India	Branch Office	192.168.11.0/24	T1
India	Branch Office	192.168.12.0/24	T1

Creating a Site

When creating a site, Active Directory and network administrators must decide how often AD will replicate between sites. They also must share certain information such as the line speed between the sites and the IP addresses of the servers that will be replicating. Knowing the line speed helps determine the correct cost of a site link. For the network administrator, knowing which IP addresses to expect network traffic from on certain ports is helpful when troubleshooting or monitoring the network. To create a site, the AD administrator needs a site name and subnet and also needs to know which other sites will replicate to the new site.

To create a site, follow these steps:

1.	Launch Server Manager on a domain controller.
2.	Expand the Roles folder.
3.	Expand the Active Directory Domain Services folder.
4.	Expand the Active Directory Sites and Services snap-in.
5.	Right-click the Sites container and choose New Site.

6.	Type in the name of the site and select any existing site link, as shown in Figure 1. Then click OK to create the site.  Figure 1. Creating a new site.
7.	A pop-up window might appear, stating what tasks still need to be completed to properly create a site. Read the information, take notes if necessary, and click OK.

Repeat this for each site that needs to be created. For the sample company, Table 2 lists the sites that will be created.

Table 2. Company ABC Sites
Location	Site Name
India	Jaipur
India	Mumbai
India	Goa
India	Patna

Creating Site Subnets

After you create a site, it should be listed in the console window. To complete the site creation process, follow these steps:

1.	Within the Active Directory Sites and Services snap-in, right-click the Subnets container, and choose New Subnet.
2.	Type in the address prefix in the Prefix field—for example, 192.168.3.0/24 for the Jaipur site IPv4 subnet.  Note  The address prefix is the IP address and the mask entered in network prefix notation. This is the format “IP network address/prefix length.” This is very similar to the IP address and subnet mask format. Table 3 lists some common subnet masks and their prefix length values. Table 3. Common Subnet Mask to Prefix Length Subnet Mask Prefix Length 255.0.0.0 8 255.255.0.0 16 255.255.255.0 24
3.	Select the appropriate site from the list at the bottom of the window to associate it with the new subnet.
4.	Click OK to create the new subnet.

Repeat this for each subnet in the locations. Table 4 lists the resulting entries for the sample Company ABC.

Table 4. Company ABC Sites and Subnets
Location	Site Name	Subnets
India	Jaipur	192.168.3.0/24 2001:db8:1234:5678::/64
India	Mumbai	192.168.10.0/24
India	Goa	192.168.11.0/24
India	Patna	192.168.12.0/24

Adding Domain Controllers to Sites

If a new domain controller is added to a forest, it will dynamically join a site with a matching subnet if the site topology is already configured and subnets have been previously defined. However, a preexisting domain controller will not change sites automatically, controller will not change

sites automatically, unlike workstations and member servers. A domain controller has to be moved manually if the topology changes. If an existing domain controller is being moved to a new site or the site topology or replication strategy has changed, you can follow these steps to move a domain controller to a different site:

1.	Launch Server Manager on a domain controller.
2.	Expand the Roles folder.
3.	Expand the Active Directory Domain Services folder.
4.	Expand the Active Directory Sites and Services snap-in.
5.	Expand the Sites folder.
6.	Locate the site that contains the desired domain controller to move. You can browse the site servers by expanding the site and selecting the Servers container of the site, as shown in Figure 2.  Figure 2. Browsing for site servers.
7.	When you locate the desired server, take note of the source site, right-click the server name, and choose Move.
8.	When a window opens listing all the sites in the forest, select the destination site, and click OK to initiate the server move.
9.	When the move is complete, verify that the domain controller has been placed in the correct Servers container of the desired site.