Sites and Subnets

Overview

The Sites and Subnets of an Active Directory define the association between domain controllers and well-connected locations. Each Site is a named collection of one or more domain controllers as well as one or more subnets. Windows devices connected to Active Directory will, by default, leverage the Site configuration to locate the nearest domain controller by performing the following steps:

1. Query Active Directory for the sites and subnets information
2. Identify the site that has a subnet value which best matches the IP address on the client
3. Select a domain controller from the site identified in the previous step

The site selection behavior can be overridden via Group Policy. The "Specify site name" policy at "Computer Configuration\Administrative Tempates\System\Net Logon" can be enabled and configured with the Site Name from the table below to force a device to use a specific site.

Site Codes

The Austin Active Directory defines three-character site codes to provide an abbreviated reference to a site. The site codes are split into two groups: campus site codes for sites associated with networks on campus and cloud site codes for sites associated with networks hosted by cloud providers. Campus site codes are simple abbreviations (aus, atx, pub, etc.) while cloud site codes follow a general rule:

• the first character is an abbreviation for the cloud provider: sites in AWS start with 'w' and sites in Azure start with 'z'
• the second and third characters are abbreviations for specific regions in the cloud provider .

Site Details

The Austin Active Directory defines multiple sites and subnets to associate domain controllers with specific physical locations both on-campus and in the cloud. 

Sites in the Austin Active Directory - Current

Sites in the Austin Active Directory - Future

References

• Designing the Site Topology | Microsoft Docs