PowerShell脚本需求：匹配IP前三段选取对应FTP服务器

Hey there! I've put together a PowerShell script that fits your exact requirements, plus breakdowns of how each part works so you can tweak it as needed:

This script runs locally on each VM, identifies which FTP server belongs to the same C-class subnet as any of the VM's IP addresses, then uses that server to transfer your large file.

# Define your list of FTP server IPs (add/remove as needed)
$ftpServers = @("10.10.10.10","10.11.10.10","10.10.12.10","10.10.10.13")

# Grab all non-loopback IPv4 addresses on the local VM (handles multi-IP setups)
$localIps = Get-NetIPAddress -AddressFamily IPv4 | Where-Object { $_.IPAddress -notlike "127.*" }

# Extract the first three octets (subnet prefix) from each local IP (for C-class /24 subnets)
$localSubnetPrefixes = $localIps | ForEach-Object {
    $octets = $_.IPAddress -split "\."
    "$($octets[0]).$($octets[1]).$($octets[2])"
}

# Find the first FTP server that shares a subnet prefix with any local IP
$targetFtpServer = $ftpServers | Where-Object {
    $ftpOctets = $_ -split "\."
    $ftpPrefix = "$($ftpOctets[0]).$($ftpOctets[1]).$($ftpOctets[2])"
    $localSubnetPrefixes -contains $ftpPrefix
} | Select-Object -First 1

# Exit if no matching FTP server is found
if (-not $targetFtpServer) {
    Write-Error "Oops! No matching FTP server found for any of the VM's subnets."
    exit 1
}

Write-Host "Successfully found matching FTP server: $targetFtpServer"

# --- Configure your file transfer details here ---
$localFilePath = "C:\Data\YourLargeFile.iso"  # Replace with your local file path
$ftpRemotePath = "/VMFiles/YourLargeFile.iso"  # Replace with the remote path on FTP
$ftpUsername = "ftp_user"  # Replace with your FTP username
$ftpPassword = "secure_password123"  # Replace with your FTP password

# Create secure credentials to avoid exposing plaintext passwords
$securePassword = ConvertTo-SecureString $ftpPassword -AsPlainText -Force
$ftpCredential = New-Object System.Management.Automation.PSCredential ($ftpUsername, $securePassword)

# Transfer the large file using WebClient (efficient for big files, streams instead of loading whole file)
try {
    $webClient = New-Object System.Net.WebClient
    $webClient.Credentials = $ftpCredential
    $fullFtpUrl = "ftp://$targetFtpServer$ftpRemotePath"

    Write-Host "Starting file transfer to $fullFtpUrl..."
    $webClient.UploadFile($fullFtpUrl, $localFilePath)
    Write-Host "File transfer completed successfully! 🎉"
}
catch {
    Write-Error "Transfer failed: $_"
}
finally {
    # Clean up the WebClient object to free resources
    if ($webClient) { $webClient.Dispose() }
}

How It Works (Key Bits Explained) #

• Multi-IP Support: The script grabs all active non-loopback IPs on the VM, so even if your VM has addresses across multiple subnets, it'll check all of them.
• Subnet Matching: For each local IP and FTP server, we split the address into octets and compare the first three (since you're using C-class 255.255.255.0 subnets). The first matching FTP server is selected.
• Secure Credentials: We convert the plaintext password to a secure string to keep sensitive data safe in memory.
• Large File Friendly: System.Net.WebClient streams the file instead of loading the entire thing into RAM, which is crucial for big files that would crash a script using simpler methods.

Quick Tweaks for Your Use Case #

• If you need to transfer to all matching FTP servers (not just the first), remove the Select-Object -First 1 line and loop through the $targetFtpServer array.
• If your FTP uses active mode instead of passive, swap out the WebClient section with FtpWebRequest and set $request.UsePassive = $false.
• Add progress tracking by using FtpWebRequest with a stream and updating a progress bar—great for extra-large files where you want to see how things are going.

内容的提问来源于stack exchange，提问作者Apps4Rent Guru