getting two ipaddress from the same FQDN - powershell

Question

I am trying to get a list of IP addresses from several servers defined in server.txt.
Each server has 2 IP addresses and 2 FQDN.
Example:
servername (Production lan):server1 IPaddress:147.111.111.16
servername (backup lan):server1-bck IPaddress:10.0.4.12
Here is the code I'm using:
$servers = Get-Content server.txt
$server2 = "$servers-bck"
$zai = ""
foreach ($server in $servers)
{
$zai = $zai + $server + "`t" +
([System.Net.Dns]::GetHostAddresses($server) | foreach {echo $_.IPAddressToString}) +
"`t" +
([System.Net.Dns]::GetHostAddresses($server2) | foreach {echo $_.IPAddressToString}) +
"`n"
}
$zai > IP-address.csv
Unfortunately only the IP for Production lan is correct. The IP for backup lan only shows the IP of the last server in server.txt. I assume the problem is in: "foreach { echo $._IPAddressToString". I don't know how to fix it.
Any idea or advice will be helpful.

Answer 1

You seem to assume that
$server2="$servers-bck"
would append -bck to the name of each element in the array $servers. That is not the case. Instead, the array is expanded by joining its elements using the output field separator, so that -bck ends up after the last array element:
PS C:\> $a = 'a', 'b', 'c'
PS C:\> $a
a
b
c
PS C:\> "$a-bck"
a b c-bck
To get the backup server for each server from your list you need to append -bck inside the loop:
...([System.Net.Dns]::GetHostAddresses("$server-bck"))...
As a side-note, you shouldn't build CSVs manually. Let PowerShell do that for you:
$servers | % {
New-Object -Type PSObject -Property #{
'Name' = $_
'Production' = ([Net.Dns]::GetHostAddresses($_) | select -Expand IPAddressToString) -join ' '
'Backup' = ([Net.Dns]::GetHostAddresses("$_-bck") | select -Expand IPAddressToString) -join ' '
}
} | Export-Csv 'IP-address.csv' -NoType -Delimiter "`t"