Query site for given ip from AD sites and services

Question

Windows Active Directory maintains a list of subnet to sites assignments (in "Active Directory - Sites and Services" -> Sites -> Subnets). The subnet-to-site associationas ar used, obviously, by workstations in order to select a suitable DC to authenticate with. But how can this information be used programmatically for other purposes? For example: Given an IP, I would like to obtain things like the Site name as found in the properties in the best matching subnet. With what have found so far, I could list all subnets and do the subnet matching with all of them myself - but as this task is in one way or other performed with every workstation reboot, I am sure that there is some direct method for this ...

Answer 1

nltest /server:servername /dsgetsite will give you the site name by querying AD.

You could wrap it in Powershell to use it programmatically more easily:

function Get-SystemSite($SystemName)
{
    $site = nltest /server:$SystemName /dsgetsite 2>$null
    if($LASTEXITCODE -eq 0) { $site[0] }
}

Answer 2

I wrote this function to simplify my use of nltest as phoebus suggested.

Function Get-AdSiteAndSubnetFromIP {
<#
.Synopsis
Get the matching AD Site and Subnet for a given IP Address
.DESCRIPTION
Get the matching AD Site and Subnet for a given IP Address.  The results will be returned as a Hash.
.EXAMPLE
Get-AdSiteAndSubnetFromIP -ip 172.28.68.53

ADSite        ADSubnet     
------        --------     
SiteA         10.1.0.0/16
.EXAMPLE

(Get-AdSiteAndSubnetFromIP -ip 172.28.68.53).ADSite

SiteA
#>
    param([string]$ip
        )
    $site = nltest /DSADDRESSTOSITE:$ip /dsgetsite 2>$null
    if ($LASTEXITCODE -eq 0) {
        $split = $site[3] -split "\s+"
        # validate result is for an IPv4 address before continuing
        if ($split[1] -match [regex]"^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$") {
            "" | select @{l="ADSite";e={$split[2]}}, @{l="ADSubnet";e={$split[3]}}
        }
    }
}