vnet.json

       {
    "$schema": "http://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
    "contentVersion": "1.0.0.0",
    "parameters": {
        "vnetName": {
            "defaultValue": "vnet",
            "type": "string",
            "metadata": {
                "description": "Name for the virtual network"
            }
        },
        "addressPrefix": {
            "defaultValue": "10.0.0.0/16",
            "type": "string",
            "metadata": {
                "description": "address range for the virtual network in CIDR notation"
            }        },
        "DBSubnetName": {
            "defaultValue": "dbsubnet",
            "type": "string",
            "metadata": {
                "description": "subnet name for database tier"
            }
        },
        "DBSubnetPrefix": {
            "defaultValue": "10.0.0.0/24",
            "type": "string",
            "metadata": {
                "description": "subnet address range for database tier in CIDR notation"
            }            
        },
        "AppSubnetName": {
            "defaultValue": "appsubnet",
            "type": "string",
            "metadata": {
                "description": "subnet name for app tier"
            }            
        },
        "AppSubnetPrefix": {
            "defaultValue": "10.0.1.0/24",
            "type": "string",
            "metadata": {
                "description": "subnet address range for app tier in CIDR notation"
            }            
        },
        "MgtSubnetName": {
            "defaultValue": "mgtsubnet",
            "type": "string",
            "metadata": {
                "description": "subnet name for shared services tier"
            }            
        },
        "MgtSubnetPrefix": {
            "defaultValue": "10.0.2.0/24",
            "type": "string",
            "metadata": {
                "description": "subnet address range for shared services tier in CIDR notation"
            }            
        }
    },
    "variables": {

    },
    "resources":   [{
            "type": "Microsoft.Network/virtualNetworks",
            "name": "[parameters('vnetName')]",
            "apiVersion": "2015-06-15",
            "location": "[resourceGroup().location]",
            "properties": {
                "addressSpace": {
                    "addressPrefixes": [
                        "[parameters('addressPrefix')]"
                    ]
                },
                "subnets": [
                    {
                        "name": "[parameters('DBSubnetName')]",
                        "properties": {
                            "addressPrefix": "[parameters('DBSubnetPrefix')]"
                        }
                    },
                    {
                        "name": "[parameters('AppSubnetName')]",
                        "properties": {
                            "addressPrefix": "[parameters('AppSubnetPrefix')]"
                        }
                    },
                    {
                        "name": "[parameters('MgtSubnetName')]",
                        "properties": {
                            "addressPrefix": "[parameters('MgtSubnetPrefix')]"
                        }
                    }                    
                ]
            }
        }
    ]
}