Add Portal instructions for duplicating NSG rules

Author: andreamichaelmsft

articles/virtual-network/manage-network-security-group.md

@@ -303,6 +303,28 @@ az network nsg rule create --resource-group myResourceGroup --nsg-name myNSG --n
     --destination-address-prefixes '*' --destination-port-ranges 3389 --protocol Tcp --description "Allow RDP"
 ```
 
+#### Duplicate security rules
+
+To duplicate existing security rules, you can export the JSON of the existing NSG, extract the `securityRules`, and include it in your ARM template.
+
+# [**Portal**](#tab/network-security-group-portal)
+
+1. In the search box at the top of the portal, enter **Network security group**. Then select **Network security groups** in the search results.
+
+1. Select the name of the NSG for which you want to duplicate the rules.
+
+1. In the NSG's **Overview** page, expand the **Essentials** section and select the **JSON View** link on the far right.
+
+1. In the **Resource JSON** half-pane, find `"properties"`. Within `"properties"`, find `"securityRules"`. Copy the full object of the security rule(s) you want to duplicate.
+
+1. In the search box at the top of the portal, enter **Deploy a custom template** and select it in the search results.
+
+1. In the **Custom deployment** page, select **Build your own template in the editor**.
+
+1. In the **Edit template** page, specify the existing NSG where you want to duplicate the rules to through its name and location. Within the `"properties"` -> `"securityRules"` of the NSG, paste the copied security rule object(s).
+
+1. Select **Save**. Select the desired subscription, resource group, and region, then select **Review + create**.
+
 ---
 ### View all security rules