It almost snuck by me but on November 15th, 2020 Microsoft announced that a web app in Azure App Service now supports NAT Gateway. That might not seem like a big deal but it can come in quite handy! Also, we have been waiting for this for quite a while.
Why is this useful?
For one the NAT Gateway provides a dedicated, fixed IP address for outgoing traffic. That can be quite handy for whitelisting use cases. You could use Azure Firewall if you want to control egress traffic over a dedicated fixed IP address by FQDN but then you miss out on the second benefit, scalability. On top of that Azure Firewall is expensive overkill just to get a dedicated IP for outbound traffic.
An Azure NAT Gateway also helps with scaling the web application. Because it delivers 64000 outbound SNAT usable ports. The Azure App Service itself has a limited number of connections you can have to the same address and port.
How to use a NAT Gateway with Azure App Service
Integrate your app with an Azure virtual network. You need to use Regional VNet Integration in order to leverage an Azure NAT Gateway. Regional VNet Integration is available for web apps in a Standard, Premium V2 or Premium V3 App Service plan. It will work with both Function apps and web or API apps. Note some Standard App Service plans cannot use Regional VNet Integration if they run on older App Service deployments on older hardware stamps. See Clarify if PremiumV2 is required for VNET integration.
Route all the outbound traffic into your Azure virtual network
Provision a NAT Gateway in the same virtual network and configure it with the subnet used for VNet Integration.
From now on outbound (egress) traffic initiated by your web app in Azure App Service will go out over the IP address of the NAT Gateway.
Last week, around August 26-27th 2020 Custom Route Tables in Azure Virtual WAN lit up in my Azure Tenants. Awesome news. Normally this should have happened the week of the 3d of August 2020. However, some delay happened. Now it is here is has come in silence. Which I find odd. This is a major capability that offers so much of what we need to make Azure Virtual WAN shine. But it is here, ready to shine at Microsoft Ignite
Custom Route Tables in Azure Virtual WAN
What do we have now? You can read up on Azure Virtual WAN route tables over here. I have made a video about all this which you can find on my blog and on my Vimeo channel. Please take a look for some walkthroughs and links to some other blog posts by me on Azure Virtual WAN.
First of all, let’s discuss the labels. Labels logically group route tables. These are very helpful when propagating routes from connections to multiple route tables. The Default Route Table has a built-in label called ‘Default’. When you propagate connection routes to the ‘Default’ label, it automatically applies to all the Default Route Tables across every hub in the Virtual WAN.
Now, we can discuss associations. Each connection is associated with one route table. This means that the connection can send to the destination indicated as routes in the route table it is associated with. The routing configuration of the connection will show the associated route table. This is very important for connected VNETs. Multiple connections can be associated with the same route table. Note that all VPN, ExpressRoute, and User VPN connections are associated with the same (default) route table.
By default, all connections are associated with the Default route table in a virtual hub. Each virtual hub has its own Default route table. You can add one or more static routes to the default Route table. Static routes take precedence over dynamically learned routes for the same prefixes.
Last but not least, connections dynamically propagate routes to one or more route table. VPN, ExpressRoute, and User VPN connections propagate routes to the same set of route tables. With connections like a Site-2-Site VPN, Express Route, or Point-2-Site VPN, routes are propagated from the virtual hub to the on-premises router using BGP.
A “None” route table is also available for each virtual hub. Propagating to the None route table implies that no routes are propagated from the connection.
Some need to ask
Finally, some customers need to reach out to support in order to get Azure Virtual WAN Custom route tables to light up.
As a result, I suggest you do so to start kicking the tires and then dive in deeper. This is a cornerstone technology for Azure networking going forward.
I have not found any documentation or guidance in regards to automation with PowerShell, Azure CLI, or ARM templates yet. I expect this to be forthcoming as this is much needed. As a result, I hope we’ll see this by Microsft Ignite 2020.
Azure Virtual WAN with the secured Virtual Hub and custom route tables offers the capabilities we have been waiting for. With these capabilities in place. Azure Virtual WAN is the future of Azure virtual networking. Therefore, I fully expect to hear a lot more about it during Microsoft Ignite in September. I personally will focus on this part of networking in the coming months. It is a stock part of any Azure initiative and project in the near future.