The standard Windows hosts file (C:\Windows\System32\drivers\etc\hosts) only supports static IP-to-hostname mappings. Unlike DNS CNAME records, it doesn't natively support hostname aliasing or dynamic IP resolution. This becomes problematic when you need to redirect traffic from one host to another with frequently changing IP addresses.

Here are three practical approaches to achieve CNAME-like functionality:

1. Using PowerShell Script for Dynamic Updates

Create a PowerShell script that periodically resolves the target hostname and updates the hosts file:

# Update-HostsAlias.ps1
$aliasHost = "hostA.example.com"
$targetHost = "hostB.example.com"
$hostsPath = "$env:SystemRoot\System32\drivers\etc\hosts"

# Resolve target IP
$targetIP = (Resolve-DnsName $targetHost -Type A).IPAddress

# Update hosts file
$newEntry = "$targetIP $aliasHost"
$currentContent = Get-Content $hostsPath -ErrorAction SilentlyContinue
$updatedContent = $currentContent -replace ".*$aliasHost.*", $newEntry

if ($updatedContent -notcontains $newEntry) {
    $updatedContent += $newEntry
}

Set-Content -Path $hostsPath -Value $updatedContent -Force

2. Local DNS Server with CNAME Support

For more robust solutions, consider setting up a local DNS server:

# Example using dnsmasq on Windows (via WSL)
# Install WSL and Ubuntu, then:
sudo apt install dnsmasq
echo "cname=hostA.example.com,hostB.example.com" | sudo tee -a /etc/dnsmasq.conf
sudo service dnsmasq restart

3. Windows Native Hosts File Workaround

While limited, you can create multiple entries for the same alias:

# hosts file example
192.168.1.10  hostA.example.com  # Primary IP for hostB
192.168.1.11  hostA.example.com  # Fallback IP

Note: Windows will use the first successful connection, so this isn't true load balancing.

For production environments, consider these automation options:

• Create a scheduled task to run the PowerShell script every 5 minutes
• Use Windows Management Instrumentation (WMI) events to trigger updates
• Implement a client-side service that watches for DNS changes

When implementing these solutions:

1. Always back up your original hosts file
2. Consider file permissions (run scripts as admin)
3. Be aware of DNS caching behavior
4. For critical systems, use proper DNS infrastructure

The Windows hosts file (located at C:\Windows\System32\drivers\etc\hosts) traditionally requires static IP mappings in this format:

192.168.1.100   myserver.local

This becomes problematic when you need to:

• Reference dynamic IP addresses that change frequently
• Create aliases that point to other hostnames rather than IPs
• Maintain multiple environments with different endpoints

While the hosts file doesn't natively support CNAME-like functionality, here are practical alternatives:

Option 1: Batch Script Automation

Create a script that resolves the target hostname and updates the hosts file:

@echo off
set TARGET_HOST=production-server.company.net
set ALIAS_NAME=staging-env

for /f "tokens=2 delims=[]" %%i in ('ping -n 1 %TARGET_HOST% ^| findstr "["') do (
    echo %%i    %ALIAS_NAME% >> C:\Windows\System32\drivers\etc\hosts
)

Option 2: PowerShell Dynamic Resolution

More robust solution using PowerShell with error handling:

$target = "elastic-search-cluster.aws.com"
$alias = "es-local"
try {
    $ip = [System.Net.Dns]::GetHostAddresses($target)[0].IPAddressToString
    $hostsEntry = "$ipt$alias"
    
    # Remove existing entry if present
    $content = Get-Content $env:windir\System32\drivers\etc\hosts | Where-Object { $_ -notmatch "$alias" }
    $content + $hostsEntry | Set-Content $env:windir\System32\drivers\etc\hosts -Force
} catch {
    Write-Error "Failed to resolve $target : $_"
}

For environments where IPs change frequently, set up a scheduled task to run the resolution script periodically:

schtasks /create /tn "UpdateHostAlias" /tr "powershell -File C:\scripts\update_host_alias.ps1" /sc hourly /ru SYSTEM

When the hosts file isn't sufficient:

• Local DNS Server: Run a local DNS resolver like dnsmasq
• Docker/Container Solutions: Use container networking aliases
• Network-Level Solutions: Configure proper DNS records in your network infrastructure

• UAC may prevent scripts from modifying the hosts file - run as admin
• Multiple applications may cache DNS resolutions
• Windows Defender may flag hosts file modifications
• For production environments, proper DNS configuration is recommended