Public/Split-Subnet.ps1
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<# .SYNOPSIS Breaks up a larger CIDR into small CIDRs. .DESCRIPTION Breaks up a larger CIDR into small CIDRs. .PARAMETER Subnet The Subnet Id to split .PARAMETER Prefix The network prefix of the source CIDR .PARAMETER TargetPrefix The network prefix to split the subnet into .EXAMPLE Split-Subnet -Subnet 10.2.2.0 -Prefix 24 -TargetPrefix 25 SubnetId : 10.2.2.0 BroadcastAddress : 10.2.2.127 SubnetMask : 255.255.255.128 Prefix : 25 Subnet : 10.2.2.0/25 FirstIPv4Address : 10.2.2.1 LastIPv4Address : 10.2.2.126 TotalHosts : 126 AWSFirstIPv4Address : 10.2.2.3 AWSTotalHosts : 124 SubnetId : 10.2.2.128 BroadcastAddress : 10.2.2.255 SubnetMask : 255.255.255.128 Prefix : 25 Subnet : 10.2.2.128/25 FirstIPv4Address : 10.2.2.129 LastIPv4Address : 10.2.2.254 TotalHosts : 126 AWSFirstIPv4Address : 10.2.2.131 AWSTotalHosts : 124 .LINK http://www.github.com/roberttoups/IPv4Toolbox #> function Split-Subnet { [CmdletBinding()] param ( [Parameter( Mandatory = $true )] [Alias('IPAddress', 'IPv4Address')] [ValidatePattern( '^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$' )] [String] $Subnet, [Parameter( Mandatory = $true )] [ValidateRange(8 , 30)] [Int32] $Prefix, [Parameter( Mandatory = $true )] [ValidateRange(8 , 30)] [Int32] $TargetPrefix ) begin { } process { if($TargetPrefix -lt $Prefix) { Write-Error -Message "The source -Prefix ($Prefix) must be larger than the -TargetPrefix ($TargetPrefix)" $Output = $null } else { $SubnetInformation = Get-SubnetInformation -IPv4Address $Subnet -Prefix $Prefix $TargetSubnetInformation = Get-SubnetInformation -IPv4Address $Subnet -Prefix $TargetPrefix $SubnetCount = ($SubnetInformation.TotalHosts + 2) / ($TargetSubnetInformation.TotalHosts + 2) Write-Verbose -Message "Subnet Count: $SubnetCount" $Start = (ConvertTo-Int64 -IPv4Address $SubnetInformation.'SubnetId') $Output = for ($i = 0; $i -lt $SubnetCount; $i++) { $NewSubnet = ConvertTo-IPv4 -Integer ($Start + (($TargetSubnetInformation.TotalHosts + 2) * $i)) Get-SubnetInformation -IPv4Address $NewSubnet -Prefix $TargetPrefix } } } end { return $Output } } |