Azure Private links and Endpoints

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One of the new features that was released from Microsoft the last couple of weeks was something called Azure Private Link. Private Link is a new feature which allows you to securely connect to PaaS services or a custom service internally from within a VNET. By default, PaaS services such as Storage or Web Apps are publically available using FQDN. For instance if you had a storage account and you wanted to access it from an on-premises environment the traffic would go out to the internet and then to the FQDN of the storage solution, which was regardless if you have a VPN connection to Microsoft Azure.

Private endpoint overview

What about Service Endpoints?

Now up until now, Microsoft has also had other solutions for connecting to PaaS services securely from the inside using Service Endpoints. Now unlike Service Endpoints, Private Endpoints can be published across tenants meaning that I can as a service provider publish endpoints into another tenant and also Service Endpoints connections are still using the public FQDN while Private Links are internally routed.

As of the preview is now, the following services are supported for Private Links
• Azure SQL
• Azure SQL Datawarehouse
• Azure Cosmos DB
• Azure Data Lake Gen 2
• Azure Storage
• Private Link Service (Which can be any service from for instance a service provider behind a standard load balancer)
* More services planned, but are coming in a later stage.

Now an interesting piece about the last part here is that Private Link Serivce allows service providers to provide services within a customer VNET. The services they can provide can be anything that is supported behind a Azure Internal Standard Load Balancer, which can be anything TCP related service.

NB: It is important to note that Private Link Services can only be TCP based & IPv4 based.

As seen beneath here is an example of a service connection using Private Endpoint within a customer tenant, where they are consuming services from both PaaS and a Private Link Service from a Service Provider. When you create a Private Endpoint you essentially create a NIC with a Private IP within your VNET which is then connected to a backend servicev running within the MSP vNET.

The Service One which sits within an MSP VNET can have any IP address they like which is then connected to a private endpoint link within customer tenant. So no need to worry about overlapping IP address segments across tenants. the Service Link handles that automatically.

When you setup a connection to a Private Link is can either be done Automatically (If you have the correct permissions) or Manually (Last part is if you are going to connect to a service provider service) And creating a private link within a VNET also generates an DNS name which the service is attached to.)

Here I am connecting to a private link at a MSP using a resource ID. 

This is an example of how a service provider has multiple connections to different tenants with a private links.
Only issue now is that there is not a good way to describe the connection, unless the customer uses a specific naming standard on their end.

In this can you need to create a service endpoint which you then attach to a service endpoint using a resource ID which you can get from your service provider. The Private Link service itself cannot be created using the Portal, only Private Endpoints so you can only create the private link using the API or PowerShell as listed here –> https://docs.microsoft.com/en-us/azure/private-link/create-private-link-service-powershell

And some quick Q&A

Does the Private Endpoints require a custom subnet? No they can be in any type of subnet
Can I connect to Private Endpoint trough a VNET Peering? Yes that is supported, but as of now you will need to Deploy a single VM on the peered Virtual Network to enable the connectivity to the service
Do I need to have the Private Endpoint and the service in the same region? No you can have for instance a Private Link or a service from an MSP in one region and the Private Endpoint in another region.
What other services will be supported moving forward? The following services will be added support for Azure Cosmos DB, Azure MySQL, Azure PostgreSQL, Azure MariaDB, Azure Application Service, and Azure Key Vault

And just be aware of the current limitations when it comes to the amount of private links that you can have

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About the Author: Marius Sandbu

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