Powershell Update ENI's DNS Tag

Update AWS network interface's Tag with its DNS entry (PowerShell 3.0)

Want to keep a tag that contains the DNS entry of an IP address of your ENIs?

This PowerShell function calls nslookup (Windows native) and adds a tag to ENI with the returned value.

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################################################
#
# Get all the reserved ENI in the VPC and
#  create a new tag based on the 
#  responding nslookup on the Private IP
#
#
#  (\_/)
#  (>.<)
# (")_(")
#
#################################################
# Get ENIs with ID, Status, PrivateIP, and DNS Tag
$ip_raw = aws ec2 describe-network-interfaces --filter "Name=vpc-id,Values=vpc-xxxxxxx" --query "NetworkInterfaces[*].{ID:NetworkInterfaceId,Status:Status,IP:PrivateIpAddress,DNS:TagSet[?Key=='DNS'].Value}"
# Convert this to PS Object
$ip = $ip_raw | out-string | convertfrom-json
foreach($item in $ip){
# Proceed only if DNS Tag does NOT exist
  if($item.DNS.length -eq 0){
    $error.clear()
    $dns = nslookup $item.ip
    if($error.count -eq 0){
      $name_line = $dns | ?{$_ -like 'Name*'}[0]
      $dns_name = ($name_line.split(":")[1].trim()
    }else{
      $dns_name = "None"
    }
    aws ec2 create-tags --resources $item.ID --tags "Key=DNS,Value=$dns_name"
  }
}