create-expressroute-gateway.json

{
	"$schema": "https://schema.management.azure.com/schemas/2015-01-01/deploymentTemplate.json#",
	"contentVersion": "1.0.0.0",
	"parameters": {
		"location": {
			"type": "string",
			"defaultValue": "[resourceGroup().location]"
		},
		"namingPrefix": {
			"type": "string"
		},
		"existingGatewaySubnetID": {
			"type": "string"
		}
	},
	"variables": {
		"erGatewayName": "[concat(parameters('namingPrefix'),'-er-gw')]",
		"erGatewayPublicIPAddressName": "[concat(parameters('namingPrefix'), '-er-gw-pip')]"
	},
	"resources": [
		{
			"apiVersion": "2018-10-01",
			"type": "Microsoft.Network/publicIPAddresses",
			"name": "[variables('erGatewayPublicIPAddressName')]",
			"location": "[parameters('location')]",
			"properties": {
				"publicIPAllocationMethod": "Dynamic"
			}
		},
		{
			"apiVersion": "2018-10-01",
			"type": "Microsoft.Network/virtualNetworkGateways",
			"name": "[variables('erGatewayName')]",
			"location": "[parameters('location')]",
			"dependsOn": [
				"[concat('Microsoft.Network/publicIPAddresses/', variables('erGatewayPublicIPAddressName'))]"
			],
			"properties": {
				"gatewayType": "ExpressRoute",
				"sku": {
					"name": "Standard",
					"tier": "Standard",
					"capacity": 2
				},
				"ipConfigurations": [
					{
						"name": "ipconfig1",
						"properties": {
							"privateIPAllocationMethod": "Dynamic",
							"subnet": {
								"id": "[parameters('existingGatewaySubnetID')]"
							},
							"publicIPAddress": {
								"id": "[resourceId('Microsoft.Network/publicIPAddresses',variables('erGatewayPublicIPAddressName'))]"
							}
						}
					}
				]
			}
		}
	]
}