Functions/Get-SubnetSize.ps1
|
#!/usr/bin/env powershell #requires -Version 1.0 function Get-SubnetSize { <# .SYNOPSIS Returns the possible number of hosts that a subnet can contain. .DESCRIPTION This function returns the possible number of hosts that the subnet can contain, by default it excludes the Subnet ID and Broadcast addresses. Shout out to http://blog.markhatton.co.uk/2011/03/15/regular-expressions-for-ip-addresses-cidr-ranges-and-hostnames/ and https://social.msdn.microsoft.com/Forums/en-US/aab23900-e42b-43a8-bb9a-7be118f9992f/how-to-make-an-regular-expression-for-subnet-mask-2552552550-for-example?forum=regexp for regex validation patterns! Found the calculation logic online too, when I refind the links will include in shoutout. .EXAMPLE Get-SubnetSize -CIDR 192.168.1.0/24 Returns the size of the subnet CIDR 192.168.1.0/24 .EXAMPLE Get-SubnetSize -SubnetMask 255.255.0.0 Returns the size of the subnet with mask 255.255.0.0 .EXAMPLE Get-SubnetSize -SubnetMask 255.0.0.0 -IncludeSubnetIDAndBroadcastAddress Returns the size of the subnet with mask 255.0.0.0, including the id and broadcase .LINK https://github.com/poshsecurity/Posh-SubnetTools Github for project .LINK https://poshsecurity.com Posh Security Website .INPUTS Can accept strings of CIDR format from pipeline. .OUTPUTS [Long] size of the subnet. #> [CmdletBinding(DefaultParameterSetName = 'CIDR')] [OutputType([long])] Param ( # Subnet in CIDR format [Parameter(Mandatory = $True, HelpMessage = 'Subnet in CIDR format', ParameterSetName = 'CIDR', ValueFromPipeline = $True, Position = 0)] [ValidateNotNullOrEmpty()] [ValidatePattern('^(([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])\.){3}([0-9]|[1-9][0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])(\/([0-9]|[1-2][0-9]|3[0-2]))$')] [String] $CIDR, # Subnet Mask [Parameter(Mandatory = $True, HelpMessage = 'Subnet Mask', ParameterSetName = 'SubnetMask', Position = 0)] [ValidateNotNullOrEmpty()] [ValidatePattern('^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))$')] [String] $SubnetMask, # Include subnet id and broadcast address [Parameter(Mandatory = $False, Position = 1)] [switch] $IncludeSubnetIDAndBroadcastAddress ) Begin { Write-Verbose -Message ('Operating with ParameterSetName of {0}' -f $PSCmdlet.ParameterSetName) if ($PSBoundParameters.ContainsKey('IncludeSubnetIDAndBroadcastAddress')) { Write-Verbose -Message 'Will include Subnet ID and broadcase addresses' } } Process { if ($PSCmdlet.ParameterSetName -eq 'CIDR') { $RoutingMask = [int]$CIDR.split('/')[1] $Total = [long][math]::pow(2, (32 - $RoutingMask)) } else { $Octets = $SubnetMask.Split('.') $Total = 1 Foreach ($Octet in $Octets) { $Total *= 256 - $Octet } $Total = [long]$Total } # Remove 2 ip addresses unless told to include those. if (-not $PSBoundParameters.ContainsKey('IncludeSubnetIDAndBroadcastAddress')) { $Total -2 } else { $Total } } } |