##Match-Subnet2Site

Param
    (
        [string]$Subnet
    )

$IPSubnetRegEx = '\b((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|0)\b'
# $IPRegEx = '\b((25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9]?[0-9])\b'

IF ($Subnet -match $IPSubnetRegEx) 
    { Write-Output "Searching the AD forest for subnet: $Subnet " }
 ELSE
    { Write-Error "The provided subnet ($Subnet) is not valid. Please enter as follows #.#.#.0 (ex. 10.22.33.0)" }

$ADForestName = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest().Name
$DomainDNS = [System.DirectoryServices.ActiveDirectory.Domain]::GetCurrentDomain().Name 

$ADSites = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest().Sites 
$ADSites = $ADSites | sort-Object Name
[int]$ADSitesCount = $ADSites.Count
Write-output "Searching $ADSitesCount AD Sites in $ADForestName `r"

[string]$SearchResults = "Subnet $Subnet could not be found in the current Active Directory forest ($ADForestName)"
ForEach ($ADSitesItem in $ADSites)
    {  ## OPEN ForEach ($ADSitesItem in $ADSites)
        $ADSitesItemName = $ADSitesItem.Name
        $ADSitesItemSubnetsCount = $ADSitesItem.Subnets.Count
        IF ($ADSitesItem.Subnets.Count -gt 1)
            {  ## OPEN IF ($ADSitesItem.Subnets.Count -gt 1)
                $ADSitesItemSubnetsArray = $ADSitesItem.Subnets
                Write-Verbose "The site $ADSitesItemName has $ADSitesItemSubnetsCount subnets "
                ForEach ($ADSitesItemSubnetsItem in $ADSitesItemSubnetsArray)
                    {  ## OPEN ForEach ($ADSitesItemSubnetsItem in $ADSitesItemSubnets)
                        $ADSitesItemSubnets = $ADSitesItemSubnetsItem.Name
                        $ADSitesItemSubnetSite = $ADSitesItemSubnetsItem.Site
                        $ADSitesItemSubnetLocation = $ADSitesItemSubnetsItem.Location
                        Write-Verbose "Checking Site $ADSitesItemName subnet $ADSitesItemSubnets"
                        IF ($ADSitesItemSubnets -like "*$Subnet*")
                           {  [string]$SearchResults = "The subnet $Subnet is configured as part of the AD site $ADSitesItemName ($ADSitesItemSubnetLocation)" }
                    }  ## CLOSE ForEach ($ADSitesItemSubnetsItem in $ADSitesItemSubnets) 
            }  ## CLOSE IF ($ADSitesItem.Subnets.Count -gt 1)
         ELSE
            { ## OPEN ELSE ($ADSitesItem.Subnets.Count -lt 1)
                $ADSitesItemSubnets = $ADSitesItem.Subnets[0].Name
                $ADSitesItemSubnetSite = $ADSitesItem.Subnets[0].Site
                $ADSitesItemSubnetLocation = $ADSitesItem.Subnets[0].Location
                
                Write-Verbose "Checking Site $ADSitesItemName single subnet $ADSitesItemSubnets"
                IF ($ADSitesItemSubnets -like "*$Subnet*")
                    {  [string]$SearchResults = "The subnet $Subnet is configured as part of the AD site $ADSitesItemName ($ADSitesItemSubnetLocation)" }
            } ## CLOSE ELSE ($ADSitesItem.Subnets.Count -lt 1)
        
        [array]$ADSitesItemSubnetsArray = $ADSitesItemSubnets -Split(", ")
   
    }  ## CLOSE ForEach ($ADSitesItem in $ADSites)    

return $SearchResults