Public/ConvertTo-IPv4MaskBit.ps1
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function ConvertTo-IPv4MaskBit { <# .SYNOPSIS Converts a subnet mask string to its CIDR bit count (0-32). .DESCRIPTION This function converts a subnet mask in dotted-decimal format (e.g., "255.255.255.0") to its equivalent CIDR notation bit count (e.g., 24). This is useful for network calculations and subnet operations where CIDR notation is required. .PARAMETER MaskString Specifies the IPv4 subnet mask in dotted-decimal format (e.g., "255.255.255.0"). Must be a valid subnet mask that passes the Test-IPv4MaskString validation. .INPUTS System.String You can pipe a string value representing a subnet mask to this function. .OUTPUTS System.Int32 Returns an integer between 0 and 32 representing the CIDR bit count. .EXAMPLE ConvertTo-IPv4MaskBit -MaskString "255.255.255.0" Returns 24, which is the CIDR bit count for the subnet mask 255.255.255.0. .EXAMPLE ConvertTo-IPv4MaskBit "255.255.0.0" Returns 16, which is the CIDR bit count for the subnet mask 255.255.0.0. .EXAMPLE "255.255.255.252" | ConvertTo-IPv4MaskBit Returns 30, which is the CIDR bit count for the subnet mask 255.255.255.252. .NOTES Used Functions: Name ║ Module/Namespace ═══════════════════════════════════════╬══════════════════════════════ Test-IPv4MaskString ║ EguibarIT Write-Verbose ║ Microsoft.PowerShell.Utility Get-FunctionDisplay ║ EguibarIT IPAddress ║ System.Net .NOTES Version: 1.1 DateModified: 22/May/2025 LastModifiedBy: Vicente Rodriguez Eguibar vicente@eguibar.com Eguibar IT http://www.eguibarit.com .LINK https://github.com/vreguibar/EguibarIT/blob/main/Public/ConvertTo-IPv4MaskBit.ps1 .COMPONENT Networking .ROLE Utility .FUNCTIONALITY Subnet Mask Conversion #> [CmdletBinding(SupportsShouldProcess = $true, ConfirmImpact = 'Low')] [OutputType([System.Int32])] Param ( [Parameter(Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, ValueFromRemainingArguments = $false, Position = 0)] [ValidateScript({ Test-IPv4MaskString $_ })] [String] $MaskString ) Begin { $txt = ($Variables.Header -f (Get-Date).ToString('dd/MMM/yyyy'), $MyInvocation.Mycommand, (Get-FunctionDisplay -HashTable $PsBoundParameters -Verbose:$False) ) Write-Verbose -Message $txt ############################## # Module imports ############################## # Variables Definition } #end Begin Process { $mask = ([IPAddress] $MaskString).Address for ( $bitCount = 0; $mask -ne 0; $bitCount++ ) { $mask = $mask -band ($mask - 1) } $bitCount } #end Process End { $txt = ($Variables.Footer -f $MyInvocation.InvocationName, 'returning the bits in a bitmask IPv4.' ) Write-Verbose -Message $txt } #end End } #end Function |