Azure App Service - Outbound IP addresses vs Additional Outbound IP Addresses - azure

Azure App Service has 2 types of outbound IP addresses:
Outbound IP Address:
Additional Outbound IP address:
I would like to know from the whitelisting perspective, which category do I need to use in my firewall?

As far as I know, you should whiteliste the Additional Outbound IP addresses:
An App Service app runs in an App Service plan, and App Service plans
are deployed into one of the deployment units in the Azure
infrastructure (internally called a webspace). Each deployment unit is
assigned up to five virtual IP addresses, which includes one public
inbound IP address and four outbound IP addresses. All App Service
plans in the same deployment unit, and app instances that run in them,
share the same set of virtual IP addresses. For an App Service
Environment (an App Service plan in Isolated tier), the App Service
plan is the deployment unit itself, so the virtual IP addresses are
dedicated to it as a result.
Because you're not allowed to move an App Service plan between
deployment units, the virtual IP addresses assigned to your app
usually remain the same, but there are exceptions.
Source.
So for some exceptions like if you scale your app between tier, one or more of the four outbound IP addresses may change (with some of the additional outbound IP addresses)
See: When outbound IPs change

Related

What should be the IP Address Requirement for App Service Creation?

We would like to create Azure App Service / Azure Function App resources for our new project and try to understand the IP Address Requirement. I am looking for this information so that I could allocate the subnet size accordingly.
Each App Service will just consume 1 App Address or More? I am new to App Service and haven't used the App Service before. So if someone could clarify in detail, it would be great.
I have created an App Service in our Virtual Network and I could see for Inbound Traffic one IP Address is Assigned and for Outbound, there are many IP Addresses assigned. So bit confused in allocating the IP Addresses.
There are a few IP addresses to be aware of in an App Service Environment. They are as follows:
Public inbound IP address: Used for external app traffic and management traffic in both internal and external deployments.
Outbound public IP: This is the IP address that is used as the "from" ip for connections that exit the virtual network. These connections do not go through a VPN.
Internal load balancer IP address: This address is solely used for internal purposes.
App-assigned IP-based TLS/SSL addresses: These addresses are only possible when using an external deployment and configuring IP-based TLS/SSL binding.
The App Service Environment UI in the Azure portal displays all of these IP addresses.
Please refer to these links as well for more information -
IP addresses ,
App Service Environment networking

What determines the outbound ip addresses in my app service in Azure?

I have one app service in Azure in a particular region with 5 outbound ip addresses and a second in the same region but there are 20 outbound ip addresses , which doesnt look right. One app is Premiumv2 the other is Premium V3
What determines the outbound ip addresses and the additional outbound ip addresses and can an outbound ip addresse be added by a user ?
App Service is a multi-tenant service (unless you use App Service Environments) and this service consists of gateway servers which accept the initial requests to App Services and forward them on to worker instances where your code actually lives. Those workers are the App Service Plans which are deployed to specific deployment units each of which are assigned a single inbound IP and multiple outbound IPs, the latter of which are chosen at random at runtime when an outbound request takes place.
This document covers all of the above and more about App Service IP addresses.
Based on which deployment unit your apps end up on you will get different IP addresses, also the SKU can affect the number of IP addresses as you've seen. If you scale up/down or redploy apps you can end up getting new IPs, the above doc has the full set of conditions as to when this might happen.
Depending on what you need to do you could consider using an App Service Environment which has single static IPs for inbound and outbound:
IP addresses don't change, as long as your App Service Environment is running
You can also use App Service VNET connectivity to give your App a private IP in a VNET so that you can connect it to resources privately in the VNET using private endpoints.

How can I reach a virtual IP address in my browser?

Playing with Azure App Service, I instantiated a simple web app. I tried to identify its IP address and found one in the properties of my app. It was described as 'virtual IP address'.
Trying to ping it or put it in my browser, it doesn't work and I can't find if it's an Azure configuration or a principle of virtual IP addresses... To be more precise, if I type '40.79.130.128' in my search bar, I crash on a 404 page, instead of my website page.
I read a bit on the topic, mainly what it is used for, but I don't understand if I can just reach it in my browser, because just typing it in my search bar is no use. What am I missing?
The Virtual IP address under your App Service on the blade Settings->Properties is the Shared IP.
The way IP address work in App Service is different. App Service app runs in an App Service plan, and App Service plans are deployed into one of the deployment units in the Azure infrastructure which is internally called a webspace and each of the deployment unit is assigned up to five virtual IP addresses, which includes one public inbound IP address and four outbound IP addresses.
All App Service plans in the same deployment unit, and app instances that run in them, share the same set of virtual IP addresses which means many App Services is behind same IP address hence you need to configure Custom Domain on your App Service to get it to work.
For configuring Custom domain refer to this link:
https://learn.microsoft.com/en-us/azure/app-service/app-service-web-tutorial-custom-domain
Please refer to below articles for details:
Inbound and outbound IP addresses in Azure App Service
App Service networking features

Mapping Outbound IPs to 1 IP in Azure App Services

I have 3 components of my architecture running in 3 separate Azure App Services. Each app service has 4 outbound IPs. So whenever I have to deploy my app onto the client's premise, I have to whitelist 12-16 IPs on their on-premise Firewall.
Is there any way I can deploy a NAT which uses only 1 public IP and I can provide just 1 IP to the client?
If I manage to make this architecture work then how would I modify my API calls to these services, since at the moment I'm using their 1 public IP to access their individual service, with just 1 IP how will I distinguish API calls made to different app service.
You can use Regional VNet Integration for your 3 App Services:
https://azure.github.io/AppService/2020/02/27/General-Availability-of-VNet-Integration-with-Windows-Web-Apps.html
Then, on the delegated subnets you can throw a User Defined Route so it goes to Azure Firewall (or any NVA) and the firewall will SNAT outbound traffic so you end up with a single outbound IP.

Keeping my out bound IPs on App Service

I have a website on Azure App service and I've asked a service provider to open up for my outbound IP addresses. How can I make sure that those IPs won't change?
If there is a new IP assigned to my app service, all calls from that IP will be blocked by the service provider.
The outbound IP addresses are per stamp/scale unit that the apps are on. It is not specific to a certain webspace or resource group.
You can find the stamp/scale unit in the Properties blade under the FTP Hostname endpoint. It should list out something like "waws-prod--". All of the apps in the same stamp/scale unit number in that region will have the same outbound IP addresses, as they are per stamp/scale unit.
The list of outbound IP addresses is not completely static but normally it does not change. Check out the reasons for the IP change in the thread outlined by Ruslan.
If you need both incoming and outgoing to be static, you will need an App Service Environment. This will give you dedicated IP addresses.
For more information see: https://learn.microsoft.com/en-us/azure/app-service/environment/app-service-app-service-environment-intro and https://msdn.microsoft.com/en-us/magazine/mt793270.aspx.

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