Merge pull request #301963 from MSFT-FrankLpnsk/Hub-Address

[Virtual WAN] Hub Address Space Cannot be changed

Author: prmerger-automator[bot]

articles/virtual-wan/hub-settings.md

@@ -112,6 +112,23 @@ Previously, there wasn't a configuration option for you to use to influence rout
 
 For more information, see [About virtual hub routing preference](about-virtual-hub-routing-preference.md).
 
+## <a name = "addressspace"></a>Virtual hub address space
+The recommended address space for a Virtual WAN hub is **/23**. It's important to note that the hub address space **cannot be modified after the hub is created**. To change the hub address space, you must redeploy the virtual hub, which can result in downtime.
+
+The Virtual WAN hub automatically assigns subnets from the specified address space to various Azure services, including:
+
+- Virtual Hub Router
+- ExpressRoute
+- Site-to-site VPN
+- Point-to-site VPN
+- Azure Firewall
+
+For scenarios where Network Virtual Appliances (NVAs) are deployed inside the virtual hub, an additional subnet is allocated for the NVA instances. Typically, a **/28 subnet** is assigned for a small number of NVAs. However, if multiple NVAs are provisioned, a **/27 subnet** might be allocated.
+
+To accommodate future scalability and architectural needs, while the minimum address space for a Virtual WAN hub is **/24**, it is recommended to specify a **/23 address space** during hub creation.
+
+For more information related to the Virtual WAN hub address space, see [Virtual WAN FAQ](virtual-wan-faq.md)
+
 ## <a name="gateway"></a>Gateway settings
 
 Each virtual hub can contain multiple gateways (site-to-site, point-to-site User VPN, and ExpressRoute). When you create your virtual hub, you can configure gateways at the same time, or create an empty virtual hub and add the gateway settings later. When you edit a virtual hub, you'll see settings that pertain to gateways. For example, gateway scale units.
@@ -120,6 +137,7 @@ Gateway scale units are different than routing infrastructure units. You adjust
 
 For more information about gateway settings, see [Gateway settings](gateway-settings.md).
 
+
 ## <a name="type"></a>Basic and Standard
 
 The virtual WAN type (Basic or Standard) determines the types of resources that can be created within a virtual hub. This includes the type of gateways that can be created (site-to-site VPN, point-to site User VPN, and ExpressRoute). This setting is configured on the virtual WAN object. For more information, see [Upgrade from Basic to Standard](upgrade-virtual-wan.md).

articles/virtual-wan/virtual-wan-faq.md

@@ -396,8 +396,19 @@ The Virtual WAN hub drops routes with an ASN of 0 in the AS-Path. To ensure thes
 Yes. This option is currently available via PowerShell only. The Virtual WAN portal requires that the hubs are in the same resource group as the Virtual WAN resource itself.
 
 ### What is the recommended hub address space during hub creation?
+The recommended address space for a Virtual WAN hub is **/23**. It's important to note that the hub address space **cannot be modified after the hub is created**. To change the hub address space, you must redeploy the virtual hub, which can result in downtime.
 
-The recommended Virtual WAN hub address space is /23. Virtual WAN hub assigns subnets to various gateways (ExpressRoute, site-to-site VPN, point-to-site VPN, Azure Firewall, Virtual hub Router). For scenarios where NVAs are deployed inside a virtual hub, a /28 is typically carved out for the NVA instances. However if the user  provisions multiple NVAs, a /27 subnet might be assigned. Therefore, keeping a future architecture in mind, while Virtual WAN hubs are deployed with a minimum size of /24, the recommended hub address space at creation time for user to input is /23.
+The Virtual WAN hub automatically assigns subnets from the specified address space to various Azure services, including:
+
+- Virtual Hub Router
+- ExpressRoute
+- Site-to-site VPN
+- Point-to-site VPN
+- Azure Firewall
+
+For scenarios where Network Virtual Appliances (NVAs) are deployed inside the virtual hub, an additional subnet is allocated for the NVA instances. Typically, a **/28 subnet** is assigned for a small number of NVAs. However, if multiple NVAs are provisioned, a **/27 subnet** might be allocated.
+
+To accommodate future scalability and architectural needs, while the minimum address space for a Virtual WAN hub is **/24**, it is recommended to specify a **/23 address space** during hub creation.
 
 ### Is there support for IPv6 in Virtual WAN?