Why do we have to create a new subnet or add the app service to an empty subnet in our vnet?
I don't understand the reasoning since I'm trying to use my app service (function app) as a reverse proxy to access the resources in the vnet.
By default, the Azure function is a PaaS as the other Azure Platform-as-a-Services that have inbound and outbound traffic over the Internet. We can host our applications without the need to worry about the maintenance of the servers and their operating systems.
To use Azure Functions to connect to resources in an Azure virtual network, we can use the VNet integration feature. To use this feature, we need to create a subnet in the virtual network for your function app to use. VNet Integration must be configured to use an empty subnet. It doesn't matter that your functions use a different subnet than your VM. The virtual network automatically routes traffic between the two subnets. Read Connect your function app to the virtual network
The extra empty subnet is used to hosting your app instance. To let the app instance outbound traffic work like from a VNet, Azure mounts NICs with assigned private IP addresses in that subnet. With VNet integration, your function app is connected to both the internet and your virtual network.
For more information, you may read How regional VNet Integration works and How gateway-required VNet Integration works
For an app to access resources in a Virtual Network, it needs to be either part of that network, or use a VPN gateway, which in turn can be used access resources inside the Virtual Network.
App Services provides 2 methods to communicate with resources in the Virtual Network:
Regional VNet Integration
Gateway-Required VNet Integration
With Regional VNet Integration, the infrastructure allocates a private IP interface on the VM that is hosting your Web App. This interface is allocated an IP address from the integrated subnets address prefix. This interface is later used to communicate with the VNet hosted resources. This is in a way similar to how IaaS VM work, however the limitation of this interface is that it can be only used for making outbound connections.
This way, if the ASP is configured to scale out to multiple VM's then each VM is allocated a corresponding private IP interface. However, the allocation of these IP address is limited to the subnets Address prefix. Nancy has already included this in her post. App Services have overlapped recycling so during scale up/maintenance, the App Service Plan may run on twice the number of VM's to ensure minimal downtime. However this also means, that the Integrated Subnet should have sufficient addresses available, so that these allocations can happen.
The IP Address of this interface is exposed via the environment variable WEBSITE_PRIVATE_IP. Here is a screenshot of my Kudu Console
If your site is running on multiple instances, then you can use the Instance menu to toggle through the instances.
With Gateway-required VNet Integration, there is a pre-requisite of provisioning a Virtual Network route-based gateway configured with an SSTP point-to-site VPN. In this case, the VM's hosting the Web App download the VPN package on the respective VM's to setup a VPN, and this is used to connect to the resources in the Virtual Network.
Even here, you can use the WEBSITE_PRIVATE_IP environment variable to see the IP Address used by the VPN client on the App Service VM.
HTH,
Kaushal
Related
We deploy to Azure app services and to ensure secure traffic between each service they are configured with out bound traffic on a virtual network subnet. Each app service must have it's own subnet, which is understandable, but to allow the app services to communicate we are having to add inbound ip restrictions for each subnet, on each app service.
As all the subnets for all the app services within an environment are on the same virtual network we were expecting the traffic to route between the subnets. In that way by connecting each app service to an out bound subnet and allowing traffic back in on that subnet it would also allow traffic from the other subnets of the virtual network.
I've read here Azure: Routing between subnets a response that state "Azure routes traffic between all subnets within a virtual network, by default. You can create your own routes to override Azure's default routing." but that does not appear to be happening for us.
Is there a setting we need to change or a route that must be added to allow us to have a single inbound rule from the virtual network that allows all traffic from all subnets of the virtual network.
We are splitting our process into micro app services but this is making security of inter-app traffic complex as each time we add an app service we must update all others with an additional inbound rule before it can communicate.
We also have a similar issue with managing access to the azure sql database where we have connected the sql to a subnet in the virtual network but traffic from the app services cannot access over that subnet.
Any advice please?
I have created a Virtual Network next to its subnet and integrated it into three service applications and created the rule on the firewall of my SQL Azure server.
Everything is in the same Azure subscription and region
I need to know if it is enough to direct all the traffic between these instances through the virtual network or do I need to configure some other aspect.
And how can I query the data traffic to verify that the virtual network is being used?
Azure Virtual Network (VNets) allows to place Azure resources in a non-internet-routable network.
https://learn.microsoft.com/en-us/azure/architecture/example-scenario/private-web-app/private-web-app#architecture
Using Azure App Service regional VNet Integration, the web app connects to Azure through an AppSvcSubnet delegated subnet in an Azure Virtual Network.
Virtual Network only routes traffic and is otherwise empty, but other subnets and workloads could also run in the Virtual Network.
The App Service and Private Link subnets could be in separate peered Virtual Networks, for example as part of a hub-and-spoke network configuration. For regional VNet Integration, the peered Virtual Networks must be located in the same Azure region.
Azure Private Link sets up a private endpoint for the Azure SQL database in the PrivateLinkSubnet of the Virtual Network.
The web app connects to the SQL Database private endpoint through the PrivateLinkSubnet of the Virtual Network.
The database firewall allows only traffic coming from the PrivateLinkSubnet to connect, making the database inaccessible from the public internet.
An Azure support engineer suggested that I put two app services on the same VNET in order to optimize my traffic. I'm new to VNETs so I'm trying to grok how this works. So far I've successfully added both the app services to the same VNET. However, it's unclear to me if it's "working" or not. I've tried reading the docs but they are incredibly dense and difficult for me to see the forest for the trees. So here's where I'm at:
Based on what I've read it seems like if services are in the same VNET the traffic between them will be routed differently. For example, say I have two services: service1.mydomain.com and service2.mydomain.com. Service 1 makes calls to service 2 via the service2.mydomain.com url. Normally, that traffic would go all the way back out to the internet and back in. But it sounds like just by adding them to the same VNET the traffic is somehow routed differently on an optimized and cheaper path. Is that accurate or is there more configuration required? If so, how can I verify that it's working?
Thanks!
It depends on the App Service Plan you're using for your App Service. If you're using Azure App Services on an App Service Environment, you'll have your own VNet for routing and it should work like that (I'm not too familiar with ASEs)
However, if you're using a Premium or lower tier, VNet integration is only useful for outbound calls, meaning that an App Service will be able to access resources on that VNet, but other integrated App Services are not on that VNet, they are just able to access resources on it as well (https://learn.microsoft.com/en-us/azure/app-service/web-sites-integrate-with-vnet).
If you want the App Services to be accessed through that VNet you'll need to set up Service Endpoints or Private Endpoints. See https://learn.microsoft.com/en-us/azure/app-service/networking-features for more details
Support is correct. Since both these services are on the same VNET, traffic will not flow outside the VNET and will be optimized. This is because the default routes for all VNETs have a route with a next hop of Virtual Network.
Virtual network: Routes traffic between address ranges within the address space of a virtual network. Azure creates a route with an address prefix that corresponds to each address range defined within the address space of a virtual network. If the virtual network address space has multiple address ranges defined, Azure creates an individual route for each address range. Azure automatically routes traffic between subnets using the routes created for each address range. You don't need to define gateways for Azure to route traffic between subnets. Though a virtual network contains subnets, and each subnet has a defined address range, Azure does not create default routes for subnet address ranges, because each subnet address range is within an address range of the address space of a virtual network.
https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview
I have created one Web app on Azure portal and its integrated with subnet under specific VNET.
Now, when I am trying to do telnet to one of my organisation's internal relay server IP from my web app its not getting connected. The request is going from web app's APIPA address range not from subnet's address range. I checked the IP as well of the web app using ifconfig and I found out that its taking from APIPA address range not from subnet one.
Any idea what steps do I need to take so that web app will take IP from subnet address range of the VNET not from APIPA address range.
Thanks in advance.
After my validation, when the app service on Linux is integrated with a virtual network. There is an extra NIC binding to the app service. It's IP address from APIPA address range. It looks like a design behavior as the app service on Linux is running in a standard Docker Container, read here. Also, for a normal app service is a multi-tenant environment, you can not get a dedicated IP address unless you are using a dedicated environment---ASE, read here.
Furthermore, from how regional VNet Integration works, you will see the app service integrated with a vNet is not the same as a VM from a VNet.
Regional VNet Integration works by mounting virtual interfaces with
addresses in the delegated subnet. Because the from address is in your
VNet, it can access most things in or through your VNet like a VM in
your VNet would. The networking implementation is different than
running a VM in your VNet. That's why some networking features aren't
yet available for this feature.
In this case, if you wan assign a private IP address for app service, you can use Azure Private Endpoint with web apps(Preview). Read this blog for more details.
Azure Private Endpoint provides private IP address access by using a
network interface controller (NIC) attached to a virtual network
subnet for an Azure web app, allowing access from an on-premise VPN or
ExpressRoute. Implementing an endpoint effectively blocks the public
inbound access. This technology is very similar to an internal App
Service Environment (ASE) but much cheaper.
Ive created an Azure app service in my VPN. My VPN has a few subnets, but I need my AppService to use just a specific subnet. Unfortunately, I can't seem to find any way of linking the AppService to a subnet. I need the traffic on that subnet to pass through a special NSG.
Any advice?
Thanks
The multi-tenant App Service connects to your VNET over Point-to-site VPN, it will use the Point-to-site address space as source IP address. Conversely, App Service Isolated (ASE/ASEv2) is deployed in a subnet inside the VNET.
Assuming multi-tenant App Service, this is how traffic flows —
There is no way to initiate traffic from the VM through the Point-to-site VPN and reach the Web App over the private channel. Only the other way around works. This limitation does not exist in App Service Isolated.
App Service Isolated —