Azure-DynamicDns.ps1

$subDomain = "redacted";
$rootDomain = "redacted";
$zoneName = $rootDomain
$resourceGroupName = $rootDomain
$secret = 'redacted';
$tenantId = 'redacted';
$applicationId = 'redacted';
$password = ConvertTo-SecureString $secret -AsPlainText -Force
$credential = New-Object System.Management.Automation.PSCredential ($applicationId, $password)

Function Get-ExternalIP {
   $ip = Invoke-RestMethod http://ip.zxq.co/self | Select -exp ip
   Return $ip
}

$domain = $subDomain+ "." + $rootDomain;
$DNSExternalIP = ((Resolve-DnsName -Name $domain -Type A -DnsOnly)[0]).IPAddress;
$CurrentIP = Get-ExternalIP
If ($CurrentIP -ne $DNSExternalIP) {
 
    Connect-AzAccount -ServicePrincipal -Credential $credential -Tenant $tenantId    
    $aRecords = @()
    $aRecords += New-AzDnsRecordConfig -IPv4Address $CurrentIP
    New-AzDnsRecordSet -Name $subDomain -RecordType A -ZoneName $zoneName -ResourceGroupName $resourceGroupName -Ttl 3600 -DnsRecords $aRecords -Overwrite 
    $message = "Updated IP for $domain to $CurrentIP successfully";    
    Write-EventLog –LogName "Application" –Source “Azure Dynamic DNS” –EntryType Information –EventID 1 –Message $message
}
Else 
{
    $message = "DNS record matches the current IP, $CurrentIP - Did not update record";    
    Write-EventLog –LogName "Application" –Source “Azure Dynamic DNS” –EntryType Information –EventID 2 –Message $message
}