Hey all,

I am trying to do a reverse DNS lookup (ip to hostname) on a list of IP's that I have in a txt file. There are ~460 addresses so I would obviously prefer not doing this manually.

After much googling, I have come up with this.

$listofIPs = Get-Content c:\iplist.txt

foreach($i in $listofips)
{
try
{
$ip = $i
$HostName = [System.Net.Dns]::GetHostByAddress($ip).HostName
Test-Connection $HostName -Count 1
}
catch
{
Write-Warning "Cannot resolve $ip"
continue
}
}

The command seems to execute but I get a "WARNING: Cannot resolve (IP Address)" error for every IP address that is in my file. It seems to parse the addresses correctly and when I use the

$IP = “(IP Address)”

[System.Net.Dns]::GetHostEntry($IP)

command, it resolves the IP just fine.

I am a complete n00b when it comes to PS and this is probably a super easy fix, but I need help! Thanks ahead of time!

What does the iplist.txt file look like? Is it just IP addresses? The scripts works well for me (I removed Test-Connection) and created an iplist.txt file:



Which outputs:



I tried with both [System.Net.Dns]::Resolve($ip) as well as [System.Net.Dns]::GetHostByAddress($ip)

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I have tried various masks for my txt file. Right now, it is just

x.x.x.x
x.x.x.x
x.x.x.x

I have also tried

"x.x.x.x"
"x.x.x.x"

as well as

"x.x.x.x",
"x.x.x.x",

Sounds like something in that file is off....what app are you using to edit the file? Notepad, word, other? And it is just one ip per line and nothing else?

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Yes, I figured out what the problem was. Jacksonh was right. When I copied the addresses out of excel into notepad, the editor I was using to answer your question, it appended a space to all of the addresses. I did a replace all on all of the spaces and copied it back into the file, then it worked just fine.

Thanks for all of your help guys.