functions/Get-NextSubnet.ps1
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<#
.SYNOPSIS Calculates the next available subnet based on a given CIDR notation. .DESCRIPTION The Get-NextSubnet function takes a subnet in CIDR notation and calculates the next available subnet with either the same prefix length or a specified one. It handles IPv4 addresses and ensures proper subnet boundary calculations. .PARAMETER CIDR Specifies the current subnet in CIDR notation (e.g., "192.168.1.0/24"). Must be a valid IPv4 CIDR notation. .PARAMETER prefixLength Specifies the prefix length for the next subnet. Must be between 1 and 32. If not specified, uses the same prefix length as the input CIDR. .EXAMPLE Get-NextSubnet -CIDR "192.168.1.0/24" Returns: "192.168.2.0/24" .EXAMPLE Get-NextSubnet -CIDR "192.168.1.0/24" -prefixLength 23 Returns: "192.168.3.0/23" .NOTES Author: PSNetworking Version: 1.1.0 Requires: get-ipcalc function .OUTPUTS System.String Returns the next subnet in CIDR notation #> Function Get-NextSubnet { param ( [ValidatePattern('^\d{1,3}(\.\d{1,3}){3}/[1-9][0-9]?$')] [string]$CIDR, [ValidateRange(1, 32)] [int]$prefixLength ) try { # Get details of the current subnet $subnetDetails = get-ipcalc $cidr | Select-Object * if (-not $prefixLength) { $prefixLength = $subnetDetails.PrefixLength } elseif ($prefixLength -lt $subnetDetails.PrefixLength) { $subnetDetails = get-ipcalc -IPAddress $subnetDetails.IPAddress -PrefixLength $prefixLength } # Retrieve necessary data $currentBaseDecimal = $subnetDetails.ToDecimal $ipCount = $subnetDetails.IPcount # Calculate the next subnet's base IP in decimal $nextBaseDecimal = $currentBaseDecimal + $ipCount # Function to convert decimal back to dotted decimal format function ConvertToDottedDecimal($decimal) { $octet1 = [math]::Floor($decimal / 16777216) $octet2 = [math]::Floor(($decimal % 16777216) / 65536) $octet3 = [math]::Floor(($decimal % 65536) / 256) $octet4 = $decimal % 256 return "$octet1.$octet2.$octet3.$octet4" } # Convert the next base IP to dotted decimal $nextBaseIP = ConvertToDottedDecimal $nextBaseDecimal # Return the next subnet in CIDR notation return "$nextBaseIP/$prefixLength" } catch { Write-Error "Failed to calculate next subnet: $_" } } |