Sends an email report with any changes made to Active Directory Sites and Subnets. Run regularly with automation.

New-ADSiteAndSubnetChangeReport.ps1

######################################################################################
##                                                                                  ##
## This script compares the current list of AD sites and subnets with a cached list ##
## If anything has changed, the cached list will be updated and the changes emailed ##
##                                                                                  ##
######################################################################################


################
## PARAMETERS ##
################

# Location of cache files
$ADSitesFile = "G:\Scheduled Task Scripts\Cache Files\ADSites.csv"
$ADSubnetsFile = "G:\Scheduled Task Scripts\Cache Files\ADSubnets.csv"

# Email parameters
$EmailParams = @{
    smtpserver =  "contoso-com.mail.protection.outlook.com"
    To = "[email protected]"
    From = "[email protected]"
    Subject = "Active Directory Site and Subnet Changes"
}

# Html CSS style
$Style = @"
<style>
table { 
    border-collapse: collapse;
}
td, th { 
    border: 1px solid #ddd;
    padding: 8px;
}
th {
    padding-top: 12px;
    padding-bottom: 12px;
    text-align: left;
    background-color: #4286f4;
    color: white;
}
</style>
"@



#################
## MAIN SCRIPT ##
#################

# ArrayLists to hold the data
$ADSites = [System.Collections.ArrayList]::new()
$ADSubnets = [System.Collections.ArrayList]::new()

# Retrieve the list of AD sites for the current forest
$Sites = [System.DirectoryServices.ActiveDirectory.Forest]::GetCurrentForest().Sites

# Retrieve the AD subnets for each AD site and convert to a custom object
foreach ($ADSite in $Sites)
{
    [void]$ADSites.Add(
        [PSCustomObject]@{
            'AD Site' = $ADSite.Name
        }
    )	
    Foreach ($Subnet in $ADSite.Subnets)
    {
        [void]$ADSubnets.Add(
            [pscustomobject]@{
                Name = $Subnet.Name
                Site = $Subnet.Site
                Location = $Subnet.Location
            }
        )
    }
}

# Test whether the cached lists exist, if not create them assuming first run
If (!(Test-Path $ADSitesFile))
{
    $ADSites | Sort 'AD Site' | Export-Csv -Path $ADSitesFile -NoTypeInformation -Force
}
If (!(Test-Path $ADSubnetsFile))
{
    $ADSubnets | Sort Name | Export-Csv -Path $ADSubnetsFile -NoTypeInformation -Force
}

# Load in the cached lists
$ADSitesCached = Import-Csv -Path $ADSitesFile
$ADSubnetsCached = Import-Csv -Path $ADSubnetsFile

# More ArrayLists to hold the data
$ADSitesAdded = [System.Collections.ArrayList]::new()
$ADSitesRemoved = [System.Collections.ArrayList]::new()
$ADSubnetsAdded = [System.Collections.ArrayList]::new()
$ADSubnetsRemoved = [System.Collections.ArrayList]::new()
$ADSubnetsModified = [System.Collections.ArrayList]::new()

# New AD sites
Foreach ($Item in $ADSites)
{
    If($Item.'AD Site' -notin $ADSitesCached.'AD Site')
    {
        [void]$ADSitesAdded.Add($Item)
    }
}

# Removed AD Sites
Foreach ($Item in $ADSitesCached)
{
    If($Item.'AD Site' -notin $ADSites.'AD Site')
    {
        [void]$ADSitesRemoved.Add($Item)
    }
}

# IP subnet where AD Site has changed, or new IP subnet added
Foreach ($Item in $ADSubnets)
{
    $Sub = $ADSubnetsCached.Where({$_.Name -eq $Item.Name})
    If ($Sub)
    {
        If ($Sub.Site -ne $Item.Site)
        {
            [void]$ADSubnetsModified.Add(
                [PSCustomObject]@{
                    Name = $Item.Name
                    OldSite = $Sub.Site
                    NewSite = $Item.Site
                }
            )
        }
    }
    Else
    {
        [void]$ADSubnetsAdded.Add($Item)
    }
}

# IP subnet removed
Foreach ($Item in $ADSubnetsCached)
{
    $Sub = $ADSubnets.Where({$_.Name -eq $Item.Name})
    If ($Sub){}
    Else
    {
        [void]$ADSubnetsRemoved.Add($Item)
    }    
}

# Prepare the HTML
If ($ADSitesAdded.Count -ge 1)
{
    $HTML1 = $ADSitesAdded | 
        ConvertTo-Html -Head $Style -Property 'AD Site' -Body "<h2>The following AD Sites have been ADDED in Active Directory</h2>" -CssUri "http://www.w3schools.com/lib/w3.css" | 
        Out-String
    
}

If ($ADSitesRemoved.Count -ge 1)
{
    $HTML2 = $ADSitesRemoved | 
        ConvertTo-Html -Head $Style -Property 'AD Site' -Body "<h2>The following AD Sites have been REMOVED from Active Directory</h2>" -CssUri "http://www.w3schools.com/lib/w3.css" | 
        Out-String
    
}

If ($ADSubnetsAdded.Count -ge 1)
{
    $HTML3 = $ADSubnetsAdded | 
        ConvertTo-Html -Head $Style -Property Name,Site,Location -Body "<h2>The following IP Subnets have been ADDED in Active Directory</h2>" -CssUri "http://www.w3schools.com/lib/w3.css" | 
        Out-String
    
}

If ($ADSubnetsRemoved.Count -ge 1)
{
    $HTML4 = $ADSubnetsRemoved | 
        ConvertTo-Html -Head $Style -Property Name,Site,Location -Body "<h2>The following IP Subnets have been REMOVED from Active Directory</h2>" -CssUri "http://www.w3schools.com/lib/w3.css" | 
        Out-String
    
}

If ($ADSubnetsModified.Count -ge 1)
{
    $HTML5 = $ADSubnetsModified | 
        ConvertTo-Html -Head $Style -Property Name,OldSite,NewSite -Body "<h2>The AD Site for the following IP Subnets has been MODIFIED in Active Directory</h2>" -CssUri "http://www.w3schools.com/lib/w3.css" | 
        Out-String
    
}

$HTML = $HTML1 + $HTML2 + $HTML3 + $HTML4 + $HTML5

# Send the email report and update the cached lists if required
If ($HTML.Length -ge 1)
{
    Try
    {
        Send-MailMessage -Body $HTML @EmailParams -BodyAsHtml -Priority High -ErrorAction Stop
    }
    Catch
    {
        $_
        Break
    }

    $ADSites | Sort 'AD Site' | Export-Csv -Path $ADSitesFile -NoTypeInformation -Force
    $ADSubnets | Sort Name | Export-Csv -Path $ADSubnetsFile -NoTypeInformation -Force
}