Subnet Toolsand other network tips

Bulk MAC address lookup

I had a list of MAC addresses and was trying to identify them by finding out as much as I could about them. This was so I could document what devices I had found on which switchports in a datacenter.

After looking them up in a router ARP table and doing a reverse DNS lookup on them I figured I’d try finding out the manufacturer to help me fill in the blanks where there was no hostname. I currently have to use Windows at work and we have a an authenticated corporate proxy.
This little powershell script takes a CSV file with a column header “MACaddress” and does a lookup against the macvendors.com API. It uses your default proxy and your default proxy credentials.

$proxy = [System.Net.WebRequest]::GetSystemWebProxy().GetProxy("http://api.macvendors.com/")

$file = import-csv "ss.csv"
foreach ($line in $file) {
	$mac = ""
	$uri = ""
	$manufacturer=""
	$mac = $line.MACaddress
	$uri = "http://api.macvendors.com/"+$mac

$manufacturer = Invoke-RestMethod -uri $uri -proxy $proxy -ProxyUseDefaultCredentials
	$output = $mac+","+$manufacturer
	echo $output
}

If you want to do the reverse DNS lookups that I did after you’ve extracted the IP from the ARP table then just use this little function in a script.

Function Get-DnsEntry($iphost)
{
 If($ipHost -match "^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$")
  {
    [System.Net.Dns]::GetHostEntry($iphost).HostName
  }
 ElseIf( $ipHost -match "^.*\.\.*")
   {
    [System.Net.Dns]::GetHostEntry($iphost).AddressList[0].IPAddressToString
   } 
 ELSE { Throw "Specify either an IP V4 address or a hostname" }
} #end Get-DnsEntry

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