Public/ConvertTo-IPv4MaskString.ps1
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function ConvertTo-IPv4MaskString { <# .SYNOPSIS Converts a CIDR bit count (0-32) to its equivalent subnet mask in dotted-decimal format. .DESCRIPTION This function converts a CIDR bit count (e.g., 24) to its equivalent subnet mask in dotted-decimal format (e.g., "255.255.255.0"). This is useful for network configurations that require subnet masks in the traditional format rather than CIDR notation. .PARAMETER MaskBits Specifies the number of bits in the subnet mask (0-32). Must be an integer between 0 and 32. .INPUTS System.Int32 You can pipe an integer value representing CIDR bit count to this function. .OUTPUTS System.String Returns a string representing the subnet mask in dotted-decimal notation. .EXAMPLE ConvertTo-IPv4MaskString -MaskBits 24 Returns "255.255.255.0", which is the subnet mask for a CIDR /24 network. .EXAMPLE ConvertTo-IPv4MaskString 16 Returns "255.255.0.0", which is the subnet mask for a CIDR /16 network. .EXAMPLE 30 | ConvertTo-IPv4MaskString Returns "255.255.255.252", which is the subnet mask for a CIDR /30 network. .NOTES Used Functions: Name ║ Module/Namespace ═══════════════════════════════════════╬══════════════════════════════ Write-Verbose ║ Microsoft.PowerShell.Utility Get-FunctionDisplay ║ EguibarIT Math.Pow ║ System BitConverter.GetBytes ║ System .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-IPv4MaskString.ps1 .COMPONENT Networking .ROLE Utility .FUNCTIONALITY Subnet Mask Conversion #> [CmdletBinding(SupportsShouldProcess = $true, ConfirmImpact = 'Low')] [OutputType([string])] Param ( [Parameter(Mandatory = $true, ValueFromPipeline = $true, ValueFromPipelineByPropertyName = $true, ValueFromRemainingArguments = $false, Position = 0)] [ValidateRange(0, 32)] [System.Int32] $MaskBits ) 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 = ([Math]::Pow(2, $MaskBits) - 1) * [Math]::Pow(2, (32 - $MaskBits)) $bytes = [BitConverter]::GetBytes([UInt32] $mask) (($bytes.Count - 1)..0 | ForEach-Object { [String] $bytes[$_] }) -join '.' } #end Process End { $txt = ($Variables.Footer -f $MyInvocation.InvocationName, 'converting bits to a networkmask string.' ) Write-Verbose -Message $txt } #end End } #end Function |