New

DDI/Get-DhcpOptions.ps1

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+function Get-DhcpOptionUsed {
+    <#
+    .SYNOPSIS
+    Check for the usage of specific DHCP option IDs in any context on a DHCP server.
+
+    .DESCRIPTION
+    Check for the usage of specific DHCP option IDs in any context on a DHCP server, including DHCP server options, scope options, and reservation options. Check all DHCP options used on a server, including server options, scope options, and reservation options.
+
+    .PARAMETER Server
+    The hostname of a DHCP server to inspect.
+
+    .EXAMPLE
+    Get-DhcpOptionUsed -Server 'dhcpserver1'
+
+    This example checks the server options, scope options, and reservation options on the DHCP server named 'dhcpserver1'.
+
+    .NOTES
+    While this currently checks for options related to DNS/name servers and NTP servers, it could be expanded with parameters to provide groups of checks for different types of options.
+    #>
+    [CmdletBinding()]
+    param (
+        # DHCP Server Name
+        [Parameter(Position = 0)]
+        [ValidateNotNullOrEmpty()]
+        [string]
+        $Server = 'localhost'
+    )
+
+    begin {
+        # Get the server's hostname if localhost is specified.
+        if ($Server -eq 'localhost') {
+            $Server = $env:COMPUTERNAME
+        }
+
+        # Check if the $Server is listed in the objects returned by Get-DhcpServerInDC.
+        $DhcpServers = Get-DhcpServerInDC
+        if ($DhcpServers.ServerName -notcontains $Server) {
+            Write-Warning -Message "The server `'$Server`' is not an authorized DHCP server in the domain."
+            return
+        }
+
+        # Verify that the server is reachable.
+        try {
+            $null = Test-NetConnection -ComputerName $Server -Count 1 -ErrorAction Stop
+        } catch {
+            Write-Error "Unable to connect to server: $Server"
+            return
+        }
+
+        # Define the options to check
+        $DhcpOptionList = [ordered]@{
+            6  = 'DNS Servers'
+            42 = 'NTP Servers'
+            44 = 'WINS/NBNS Servers'
+        }
+        $OptionsToCheck = $DhcpOptionList.Keys
+    } # end begin block
+
+    process {
+        # Get all IPv4 DHCP server options and check the options set on each.
+        Write-Host 'Checking DHCP Server Options....' -ForegroundColor Green -BackgroundColor Black
+        $ServerOptions = Get-DhcpServerv4OptionValue
+        foreach ($option in $ServerOptions) {
+            if ($OptionsToCheck -contains $option.OptionId) {
+                Write-Host ".... > Server has option $($option.OptionId) set." -ForegroundColor Magenta -BackgroundColor Black
+            }
+        } # end foreach server option
+
+        # Get all IPv4 DHCP scopes and check the options set on each.
+        Write-Host 'Checking DHCP Scope Options....' -ForegroundColor Green -BackgroundColor Black
+        $v4Scopes = Get-DhcpServerv4Scope
+        foreach ($scope in $v4Scopes) {
+            # Check scope options first.
+            Write-Host "....Checking Scope: $($scope.ScopeId)" -ForegroundColor Yellow -BackgroundColor Black
+            $ScopeOptions = $null
+            $ScopeOptions = Get-DhcpServerv4OptionValue -ScopeId $scope.ScopeId
+            foreach ($option in $ScopeOptions) {
+                if ($optionsToCheck -contains $option.OptionId) {
+                    Write-Host ".... > Scope $($scope.ScopeId) has option $($option.OptionId) set." -ForegroundColor Magenta -BackgroundColor Black
+                }
+            } # end foreach scope option
+
+            # Check reservation options.
+            $v4Reservations = Get-DhcpServerv4Reservation -ScopeId $scope.ScopeId
+            foreach ($reservation in $v4Reservations) {
+                Write-Host "....Checking Reservation: $($reservation.IPAddress)" -ForegroundColor Yellow -BackgroundColor Black
+                $ReservationOptions = $null
+                $ReservationOptions = Get-DhcpServerv4OptionValue -ScopeId $scope.ScopeId -ReservedIP $reservation.IPAddress
+                foreach ($option in $ReservationOptions) {
+                    if ($optionsToCheck -contains $option.OptionId) {
+                        Write-Output ".... > Reservation $($reservation.IPAddress) in scope $($scope.ScopeId) has option $($option.OptionId) set."
+                    }
+                } # end foreach reservation option
+            } # end foreach reservation
+        } # end foreach scope
+
+    } # end process block
+
+    end {
+        Write-Host "Finished checking DHCP options on $Server." -ForegroundColor Green -BackgroundColor Black
+    } # end end block
+}