VCD – Find free external IPs

Finding free public IPs in Cloud Director backed by NSX-V is not as easy as it should be. Some people will tell you to ping the scope and see what’s responding. But pinging is not reliable was of finding free IPs. Not every device is responding to ICMP messages.

Somewhere along the line, I found a guy on the VMware forum posting a script for finding available IPs in Cloud Director using the PowerCLI module for querying VCD and getting back IPs that are not allocated by an Edge. I have been using the script quite a bit since. His blog is not available today, but the code is still on the forum.

Now it’s also available here on the site with a bit more explanation on how to connect and use the function. I have been using it with NSX-V as backend, haven’t tried it with NSX-T at the network backend yet.

 ### Install PowerCLI module
Install-Module -Name VMware-vCD-Module

### Import PowerCLI Cloud module
Import-Module -Name VMware.VimAutomation.Cloud

### Connect to Cloud Director instance with your credentials
Connect-CIServer -server <VCD_URL>

Function Get-FreeExtIPAddress([String]$extnetName){
    function  Convertto-IPINT64  () { 
    param ($ip) 
    
    $octets = $ip.split(".") 
    return [int64]([int64]$octets[0]*16777216 +[int64]$octets[1]*65536 +[int64]$octets[2]*256 +[int64]$octets[3]) 
    } 
    
    function  Convertto-INT64IP() { 
    param ([int64]$int) 
    
    return (([math]::truncate($int/16777216)).tostring()+"."+([math]::truncate(($int%16777216)/65536)).tostring()+"."+([math]::truncate(($int%65536)/256)).tostring()+"."+([math]::truncate($int%256)).tostring() )
    } 
    $extnet = Get-ExternalNetwork -name $extnetName
    $ExtNetView = $Extnet | Get-CIView
    $allocatedGatewayIPs = $extnetView.Configuration.IpScopes.IpScope[0].SubAllocations.SubAllocation.IpRanges.IpRange | ForEach-Object {
        $startaddr = Convertto-IPINT64 -ip $_.StartAddress
        $endaddr = Convertto-IPINT64 -ip $_.EndAddress
        for ($i = $startaddr; $i -le $endaddr; $i++) 
        { 
            Convertto-INT64IP -int $i 
        }
    }
    [int]$ThirdStartingIP = [System.Convert]::ToInt32($extnet.StaticIPPool[0].FirstAddress.IPAddressToString.Split(".")[2],10)
    [int]$ThirdEndingIP = [System.Convert]::ToInt32($extnet.StaticIPPool[0].LastAddress.IPAddressToString.Split(".")[2],10)
    [int]$FourthStartingIP = [System.Convert]::ToInt32($extnet.StaticIPPool[0].FirstAddress.IPAddressToString.Split(".")[3],10)
    [int]$FourthEndingIP = [System.Convert]::ToInt32($extnet.StaticIPPool[0].LastAddress.IPAddressToString.Split(".")[3],10)
    $octet = $extnet.StaticIPPool[0].FirstAddress.IPAddressToString.split(".")
    $3Octet = ($octet[0]+"."+$octet[1]+"."+$octet[2])
    $2Octet = ($octet[0]+"."+$octet[1])
    $ips = @()
    if ($ThirdStartingIP -eq $ThirdEndingIP) {
        $ips = $FourthStartingIP..$FourthEndingIP | % {$3Octet+'.'+$_}
    } else {
        do {
            for ($i=$FourthStartingIP; $i -le 255; $i++) {
                $ips += ($2Octet + "." + $ThirdStartingIP + "." + $i)
            }
            $ThirdStartingIP=$ThirdStartingIP + 1
        } while ($ThirdEndingIP -ne $ThirdStartingIP)
        for ($i=0;$i -le $FourthEndingIP; $i++) {
            $ips += ($2Octet + "." + $ThirdStartingIP + "." + $i)
        }
    }
        $allocatedIPs = $ExtNetView.Configuration.IpScopes.IpScope[0].AllocatedIpAddresses.IpAddress
    for ($i=0;$i -le $ips.count; $i++) {
        for ($j=0; $j -lt $allocatedGatewayIPs.count; $j++) {
            if ($ips[$i] -eq $allocatedGatewayIPs[$j]) {
                $ips = $ips | Where-Object { $_ -ne $ips[$i] }
                $i--
            }
        }
        for($z=0;$z -lt $allocatedIPs.count;$z++) {
            if ($ips[$i] -eq $allocatedIPs[$z]) {
                $ips = $ips | Where-Object { $_ -ne $ips[$i] }
                $i--
            }
        }
    }
    return $Ips
}

### Find the names of external networks
Get-ExternalNetwork

### Find free IPs using function from above
Get-FreeExtIPAddress -extnetName <vcd-net>

You can help yourself by copy and pasting the code snip into either PowerShell ISE or VisualCode. And since you need to install a cmdlet you need to run it with elevated rights. If you get a red message with importing the module it’s probably because of execution rights, you then need to run to command beneath. This is for allowing remote signed cmdlets to be executed.

Set-ExecutionPolicy RemoteSigned