ARM Template section that shows how to update the DNS settings for a VM before it is added as a replica Domain Controller. The ip address of the first DC is added as the DNS on the virtual machine

CreateADReplicaDC_UpdateDC02Nic.json

 {
      "name": "UpdateDC02NIC",
      "type": "Microsoft.Resources/deployments",
      "apiVersion": "2015-01-01",
      "dependsOn": [],
      "properties": {
        "mode": "Incremental",
        "templateLink": {
          "uri": "[variables('nicTemplateUri')]",
          "contentVersion": "1.0.0.0"
        },
        "parameters": {
          "nicName": {
            "value": "[parameters('DC02NicName')]"
          },
          "ipConfigurations": {
            "value": [
              {
                "name": "ipconfig1",
                "properties": {
                  "privateIPAllocationMethod": "Static",
                  "privateIPAddress": "[parameters('DC02NicIPAddress')]",
                  "subnet": {
                    "id": "[variables('DC02SubnetRef')]"
                  }
                }
              }
            ]
          },
          "dnsServers": {
            "value": [
              "[parameters('DC01NicIPAddress')]"
            ]
          }
        }
      }
    },