Building a list of IP addresses - powershell

Question

I am trying to build an array of possible IP addresses based on a user's input. i.e. IP address along with a CIDR number. My end goal is to compare this list with a separate list of addresses and find which are is missing.
Example
user input: 192.168.1.0 /24
I want to build an array for all possible values for the /24 network (i.e. the IP address can be anywhere from 192.168.1.0 - 192.168.1.255)
In order for this to work, I think I have to convert the IP address to binary and then find the bits that will be the host part of the network, which I've done here:
function ConvertToBinary{
param($ipAddress)
[string]$binaryIP = -join ($ipAddress.Split('.') | ForEach-Object {[System.Convert]::ToString($_,2).PadLeft(8,'0')})
return $binaryIP
}
function FindHost{
param(
[string]$binaryIPAddress,
[int32]$CIDR
)
$hostBits = 32-$CIDR
[string]$myHost = $binaryIPAddress.Substring($binaryIPAddress.Length-$hostBits)
return $myHost
}
$myip = ConvertToBinary "192.168.3.1"
$myHost = FindHost $myip 8
I'm a little stuck on how to proceed, so if anyone can help me out or point me in the right direction, it would be much appreciated

Answer 1

I wrote this using some similar questions to get the first and last address for any subnet given a random IP and mask:
Function Get-SubnetAddresses {
Param ([IPAddress]$IP,[ValidateRange(0, 32)][int]$maskbits)
# Convert the mask to type [IPAddress]:
$mask = ([Math]::Pow(2, $MaskBits) - 1) * [Math]::Pow(2, (32 - $MaskBits))
$maskbytes = [BitConverter]::GetBytes([UInt32] $mask)
$DottedMask = [IPAddress]((3..0 | ForEach-Object { [String] $maskbytes[$_] }) -join '.')
# bitwise AND them together, and you've got the subnet ID
$lower = [IPAddress] ( $ip.Address -band $DottedMask.Address )
# We can do a similar operation for the broadcast address
# subnet mask bytes need to be inverted and reversed before adding
$LowerBytes = [BitConverter]::GetBytes([UInt32] $lower.Address)
[IPAddress]$upper = (0..3 | %{$LowerBytes[$_] + ($maskbytes[(3-$_)] -bxor 255)}) -join '.'
# Make an object for use elsewhere
Return [pscustomobject][ordered]#{
Lower=$lower
Upper=$upper
}
}
Usage looks like:
Get-IPAddresses 10.43.120.8 22
Lower Upper
----- -----
10.43.120.0 10.43.123.255
And I put this together to generate the whole list. I'm sure this could be done better, but the simple instructions run fast enough:
Function Get-IPRange {
param (
[Parameter(Mandatory=$true,ValueFromPipelineByPropertyName)][IPAddress]$lower,
[Parameter(Mandatory=$true,ValueFromPipelineByPropertyName)][IPAddress]$upper
)
# use lists for speed
$IPList = [Collections.ArrayList]::new()
$null = $IPList.Add($lower)
$i = $lower
# increment ip until reaching $upper in range
while ( $i -ne $upper ) {
# IP octet values are built back-to-front, so reverse the octet order
$iBytes = [BitConverter]::GetBytes([UInt32] $i.Address)
[Array]::Reverse($iBytes)
# Then we can +1 the int value and reverse again
$nextBytes = [BitConverter]::GetBytes([UInt32]([bitconverter]::ToUInt32($iBytes,0) +1))
[Array]::Reverse($nextBytes)
# Convert to IP and add to list
$i = [IPAddress]$nextBytes
$null = $IPList.Add($i)
}
return $IPList
}
Converting to [IPAddress] on the last line is nice for validating all the results are real, but probably not necessary if you just want the ipv4 strings. Usage:
Get-SubnetAddresses 10.43.120.8 30 | Get-IPRange | Select -ExpandProperty IPAddressToString
10.43.120.8
10.43.120.9
10.43.120.10
10.43.120.11
Sources:
https://stackoverflow.com/a/51307519/7411885
https://stackoverflow.com/a/58821442/7411885