Azure Automation to Sync DNS resolution to Route Table

Sync-RouteTableDns.ps1

Param(
  [Parameter (Mandatory = $true)]
  [sring]$DnsName,
  [string]$RouteName
)

if($RouteName -eq "") {
    $RouteName = $DnsName
}

#region Azure Automation bootstrap
try
{
    $servicePrincipalConnection = Get-AutomationConnection -Name "AzureRunAsConnection"
    "Logging in to Azure..."
    Connect-AzAccount `
        -ServicePrincipal `
        -TenantId $servicePrincipalConnection.TenantId `
        -ApplicationId $servicePrincipalConnection.ApplicationId `
        -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint 
}
catch {
    if (!$servicePrincipalConnection)
    {
        $ErrorMessage = "Connection AzureRunAsConnection not found."
        throw $ErrorMessage
    } else{
        Write-Error -Message $_.Exception
        throw $_.Exception
    }
}

$smtpCredential = Get-AutomationPSCredential -Name "SendGridCredentials"
#endregion

#region Configuration
# Azure
$routeTableResourceGroupName = "test_group"
$routeTableName = "RT-ForcedTunneling"

# Mail notifications
$smtpServer = "smtp.sendgrid.net"
$emailFrom = "Azure Automations <[email protected]>"
$emailTo = "[email protected]" # CC added to every e-mail sent by this script
#endregion

$result = [system.net.dns]::GetHostByName($dnsName)
$record = $result.AddressList | Select-Object -First 1
if(-not $record) {
    throw "Unable to resolve IP for $dnsName"
}

$description = ""
$prefix = "$($record)/32"
$routeTable = Get-AzRouteTable -ResourceGroupName $routeTableResourceGroupName -Name $routeTableName
$route = $routeTable.Routes | Where-Object Name -eq $routeName
if(-not $route) {
    Add-AzRouteConfig -RouteTable $routeTable -Name $routeName -AddressPrefix $prefix -NextHopType "Internet" | Set-AzRouteTable | Out-Null

    $description = "New route entry created in $routeTableName (RG $routeTableResourceGroupName) with address prefix $prefix."
} else {
    if($prefix -ne $route.AddressPrefix) {
        Set-AzRouteConfig -RouteTable $routeTable -Name $routeName -AddressPrefix $prefix -NextHopType Internet | Set-AzRouteTable | Out-Null

        $description = "Prefix of route $routeName in $routeTableName (RG $routeTableResourceGroupName) has been changed from $($route.AddressPrefix) to $prefix."
    }
}
$description

if($description -ne "") {
    Send-MailMessage -SmtpServer $smtpServer -Credential $smtpCredential -UseSsl -Port 587 `
                     -From $emailFrom -To $emailTo -Subject "Updated Routing Table $($routeTableName)" `
                     -Body $description -Encoding UTF8
}