<#
Check Active Directory Sites
http://blogs.metcorpconsulting.com/tech/?p=366
#>

# Set variables
[array] $SitesWithNoSubnet = @()
[array] $SitesWithNoSiteLinks = @()
[array] $SitesWithNoISTG = @()
[array] $DCsnotGC = @()
[array] $SitesWithNoGC = @()
#Get AD Domain (lightweight & fast method)
$DomainDNS = [System.DirectoryServices.ActiveDirectory.Domain]::GetCurrentDomain().Name
import-module activedirectory
Write-Verbose "Get AD Site List `r"
[array] $ADSites = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest().Sites
$ADSitesCount = $ADSites.Count
Write-Output "There are $ADSitesCount AD Sites `r"
## Check AD Sites
Write-Verbose "Checking for AD Site issues `r "
ForEach ($Site in $ADSites) {
    ## OPEN ForEach Site in ADSites
    $SiteName = $Site.Name
    [array] $SiteSubnets = $Site.Subnets
    [array] $SiteServers = $Site.Servers
    [array] $SiteAdjacentSites = $Site.AdjacentSites
    [array] $SiteLinks = $Site.SiteLinks
    $SiteInterSiteTopologyGenerator = $Site.InterSiteTopologyGenerator
    # Check for missing subnets
    IF (!$SiteSubnets) {
        ## OPEN IF there are no Site Subnets
        Write-Verbose "The site $SiteName does not have a configured subnet. `r "
        [array] $SitesWithNoSubnet += $SiteName
    }  ## OPEN IF there are no Site Subnets
    # Check for missing site link
    IF (!$SiteLinks) {
        ## OPEN IF there are no Site Links for this site
        Write-Verbose "The site $SiteName does not have an associated site link. `r "
        [array] $SitesWithNoSiteLinks += $SiteName
    }  ## OPEN IF there are no Site Links for this site
    # Check for missing ISTG
    IF (!$SiteInterSiteTopologyGenerator) {
        ## OPEN IF there are no ISTG  for this site
        Write-Verbose "The site $SiteName does not have a configured InterSite Topology Generator server `r "
        [array] $SitesWithNoISTG += $SiteName
    }  ## OPEN IF there are no ISTG for this site
    # Find AD Sites with no GCs
    $SiteDC = Get-ADDomainController -filter { (Site -eq $Site) -and (IsGlobalCatalog -eq $True) }
    IF (!$SiteDC) {
        ## OPEN IF there are no GCs for this site
        Write-Verbose "The site $SiteName does not have a Global Catalog associated with it `r "
        [array] $SitesWithNoGC += $SiteName
    }  ## OPEN IF there are no GCs for this site
}  ## CLOSE ForEach Site in ADSites
$SitesWithNoSubnetCount = $SitesWithNoSubnet.Count
IF ($SitesWithNoSubnetCount -ge 1) {
    ## IF Count is >= 1
    Write-Output "The following $SitesWithNoSubnetCount sites do not have subnets associated with them `r "
    $SitesWithNoSubnet
    Write-Output " `r "
}  ## IF Count is >= 1
$SitesWithNoSiteLinksCount = $SitesWithNoSiteLinks.Count
IF ($SitesWithNoSiteLinksCount -ge 1) {
    ## IF Count is >= 1
    Write-Output "The following $SitesWithNoSiteLinksCount sites do not have Site Links associated with them `r "
    $SitesWithNoSiteLinks
    Write-Output " `r "
}  ## IF Count is >= 1
$SitesWithNoISTGCount = $SitesWithNoISTG.Count
IF ($SitesWithNoISTGCount -ge 1) {
    ## IF Count is >= 1
    Write-Output "The following $SitesWithNoISTGCount sites do not an ISTG associated with them `r "
    $SitesWithNoISTG
    Write-Output " `r "
}  ## IF Count is >= 1
$SitesWithNoGCCount = $SitesWithNoGC.Count
IF ($SitesWithNoGCCount -ge 1) {
    ## IF Count is >= 1
    Write-Output "The following $SitesWithNoGCCount sites do not have a GC associated with them `r "
    $SitesWithNoGC
    Write-Output " `r "
}  ## IF Count is >= 1