CODEWITHSUNDEEP
c#powershellip-address
scar80
scar80

Reputation: 1702

How to check in Powershell if IP address or hostname is a localhost? Without domain DNS

I have a powershell script which runs some command on a local or remote computer. When the computer is remote then the command is called via Invoke-Command and a user is prompted for additional credentials.

A user can enter a script parameter which can be: hostname, IP, 127.0.0.1, alias from hosts file. I need to check if that parameter is for local or remote machine in order to call local command or Invoke-Command. I used to do it this way:

Function IsLocalhost {
    Param([string] $srvname)

    $script:AVLserverHost = $srvname.Split('\')[0]
    #Write-Host ("HOST: " + $script:AVLserverHost)

    if ((get-content env:computername) -eq $script:AVLserverHost) {
        return $true;
    } else {
        $AddressList = @(([net.dns]::GetHostEntry($script:AVLserverHost)).AddressList) 
        $script:HostIp = $AddressList.IpAddressToString

        $name = [System.Net.Dns]::gethostentry($script:HostIp)
        if ((get-content env:computername) -eq $name.HostName) {
            return $true
        }
    }
    return $false
}

But it only works on a domain DNS. Our computers are on a workgroup or a standalone computers that we can connect only by IP or alias from hosts file.

So how to check in powershell (or c# code) if given host is local or not, if the host is not in a domain DNS. I would like to have true/false if it is local or not and its real IP address if hostname or host alias was entered.

Upvotes: 1

Views: 4634

Answers (3)

Rosberg Linhares
Rosberg Linhares

Reputation: 3687

You can try this:

function Is-LoopBackAddress([string] $Address)
{
    $addressIPs = [Net.Dns]::GetHostAddresses($Address).IPAddressToString

    $netInterfaces = [Net.NetworkInformation.NetworkInterface]::GetAllNetworkInterfaces()

    foreach ($netInterface in $netInterfaces)
    {
        $ipProperties = $netInterface.GetIPProperties()

        foreach ($ip in $ipProperties.UnicastAddresses)
        {
            if ($addressIPs -contains $ip.Address.IPAddressToString)
            {
                return $true
            }
        }
    }

    return $false
}

Is-LoopBackAddress 'localhost'

Upvotes: 1

scar80
scar80

Reputation: 1702

I combined @Noah's code with other example how to read hosts file and this is final code:

Function IsLocalhost {
    Param([string] $srvname)

    $script:AVLserverHost = $srvname.Split('\')[0]

    #get list of localhost addresses
    $localAddresses = @()
    $localAddresses += (gwmi Win32_NetworkAdapterConfiguration | ? {$_.IPAddress}) | select -expand ipaddress | select-string -notmatch ":"
    $localAddresses += 'localhost'
    $localAddresses += '127.0.0.1'
    $localAddresses += hostname

    $hosts = "$env:windir\System32\drivers\etc\hosts"

    [regex]$r="\S"   #define a regex to return first NON-whitespace character

    #strip out any lines beginning with # and blank lines
    $HostsData = Get-Content $hosts | where {
        (($r.Match($_)).value -ne "#") -and ($_ -notmatch "^\s+$") -and ($_.Length -gt 0)
    }

    $HostsData | foreach {
        $_ -match "(?<IP>\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})\s+(?<HOSTNAME>\S+)" | Out-Null
        $ip = $matches.ip
        $hostname = $matches.hostname

        if ($localAddresses -contains $ip) {
            $localAddresses += $hostname
        }
    }

    if ($localAddresses -contains $script:AVLserverHost) {
        return $true;
    } else {
        $script:HostIp = (Test-Connection $script:AVLserverHost | Select-Object IPV4Address)[0].IPV4Address.IPAddressToString
    }
    return $false
}

Upvotes: 0

Noah Sparks
Noah Sparks

Reputation: 1762

you could generate an array of the local IP's, add localhost to the array and then see if your parameter is in the array. here is a ps2.0 compatible version for ipv4.

$LocalArray = @()
$LocalArray += (gwmi Win32_NetworkAdapterConfiguration | ? {$_.IPAddress}) | select -expand ipaddress | select-string -notmatch ":"
$LocalArray += 'localhost'
$LocalArray += '127.0.0.1'
$LocalArray += hostname
$LocalArray -contains $IP

Upvotes: 1

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