Merge pull request #212642 from madsd/subnetsize

Change message around subnet size

Author: prmerger-automator[bot]

articles/app-service/environment/networking.md

@@ -3,7 +3,7 @@ title: App Service Environment networking
 description: App Service Environment networking details
 author: madsd
 ms.topic: overview
-ms.date: 08/01/2022
+ms.date: 09/27/2022
 ms.author: madsd
 ---
 
@@ -20,6 +20,9 @@ You must delegate the subnet to `Microsoft.Web/hostingEnvironments`, and the sub
 
 The size of the subnet can affect the scaling limits of the App Service plan instances within the App Service Environment. It's a good idea to use a `/24` address space (256 addresses) for your subnet, to ensure enough addresses to support production scale.
 
+>[!NOTE]
+> Windows Containers uses an additional IP address per app for each App Service plan instance, and you need to size the subnet accordingly. If your App Service Environment has for example 2 Windows Container App Service plans each with 25 instances and each with 5 apps running, you will need 300 IP addresses and additional addresses to support horizontal (up/down) scale.
+
 If you use a smaller subnet, be aware of the following:
 
 - Any particular subnet has five addresses reserved for management purposes. In addition to the management addresses, App Service Environment dynamically scales the supporting infrastructure, and uses between 4 and 27 addresses, depending on the configuration and load. You can use the remaining addresses for instances in the App Service plan. The minimal size of your subnet is a `/27` address space (32 addresses).

articles/app-service/overview-vnet-integration.md

@@ -3,7 +3,7 @@ title: Integrate your app with an Azure virtual network
 description: Integrate your app in Azure App Service with Azure virtual networks.
 author: madsd
 ms.topic: conceptual
-ms.date: 08/01/2022
+ms.date: 09/27/2022
 ms.author: madsd
 
 ---
@@ -60,7 +60,10 @@ When you scale up or down in size, the required address space is doubled for a s
 
 <sup>*</sup>Assumes that you'll need to scale up or down in either size or SKU at some point.
 
-Because subnet size can't be changed after assignment, use a subnet that's large enough to accommodate whatever scale your app might reach. To avoid any issues with subnet capacity, use a `/26` with 64 addresses. When you're creating subnets in Azure portal as part of integrating with the virtual network, a minimum size of /27 is required.
+Because subnet size can't be changed after assignment, use a subnet that's large enough to accommodate whatever scale your app might reach. To avoid any issues with subnet capacity, use a `/26` with 64 addresses. When you're creating subnets in Azure portal as part of integrating with the virtual network, a minimum size of /27 is required. If the subnet already exists before integrating through the portal you can use a /28 subnet.
+
+>[!NOTE]
+> Windows Containers uses an additional IP address per app for each App Service plan instance, and you need to size the subnet accordingly. If you have for example 10 Windows Container App Service plan instances with 4 apps running, you will need 50 IP addresses and additional addresses to support horizontal (up/down) scale. 
 
 When you want your apps in your plan to reach a virtual network that's already connected to by apps in another plan, select a different subnet than the one being used by the pre-existing virtual network integration.