Securing and Connecting Azure Resources from On-Premise Machines

7 minute read

You want to connect your Azure resources from your on-premise office machine or home laptop right? So how would you do that? Read this article. In order to connect machine/servers residing over your on-premise office from home you need internet. You know anything over internet is not secure. So how would you secure your connection?

How can I connect machine or server residing in my on-premise office?

Well you need internet and route your connection to you office machine. For that you have to expose your office server or machine IP addresses over internet so that you can connect them. However, this will put your official data at risk. Now anyone over internet can connect your machine and stole data. Or hacker can trap your communication over internet and hack your data or machine.

How would I secure my data while connecting to on-premise Office servers?

VPN is the secure way to connect to other machines over internet. If you want to connect machine which is in your office building from your home. You need internet and the data that you will transfer from your office to your home is exposed to internet. Any malicious user can access/read/manipulate that data. In order to secure your traffic data over internet. You must need VPN connection. VPN creates a encrypted tunnel from your home laptop to the office machine. All data is isolated/encrypted using different IPSec tunnels created by VPN. Now your data over internet is secure in-transit.

How do I connect Azure Resources from my Home PC or office PC?

If you have on-premise office or home laptop to connect Azure VNet. You need VPN setup with physical device in on-premise location. And you need VPN Gateway on Azure VNet. A VPN Gateway is used when creating a VPN connection from your on-premises network.

If you want to put your azure resources in private network over cloud. You must create VNet and assign all resource to that VNet in a same region. All resources within VNet must be in one region. So you must create VNet in Azure cloud.

If you have your own on-premise office or home laptop to connect to your Azure resources. Which is in VNet you must use VPN technology to connect to your Azure resources inside VNet. You could use other options like Express Route circuit which is costly and fast option. In this article I will discuss VPN option. VPN uses internet to flow your data. However Express Route uses dedicated connection that doesn’t uses internet.

Why I need VNet in Azure?

VNet is a private network in cloud. Just like on-premise we create network. All resources inside Azure VNet can browse internet. (outbound is allowed by default) However, from internet you can not connect to the VM or any resources present within a VNet by default inbound are restricted from any public IP. In order to perform this activity you must deploy Azure Public IP resource in your VNet. Read more here.. Therefore, VNet provides isolation to your Azure resources over cloud.

πŸ† Pro Tip

I was wondering Why we are able to communicate our web apps in Azure from internet? And I found this answer promising. By default, apps hosted in App Service are accessible directly through the internet. Read more here.

What do I need in Azure Cloud to allow VPN connection?

In order to configure and allow connection of on-premise VPN to VNet in Azure ( also called as site to site or point to site ). In Azure cloud you must create Virtual Network Gateway or VPN Gateway. This VPN Gateway allows VPN traffic to flow in your Azure VNet.

In order to create Azure Virtual Network Gateway, you have to first create GatewaySubnet. Because VPN Gateway needs dedicated subnet.

πŸ† Pro Tip

Only one VPN Gateway is allowed in Azure Virtual Network (VNet)

How do I secure my Azure resources within VNet?

Now in order to restrict which traffic can flow to your Azure VNet resources. You must configure Azure Firewall or Network Security Group. To restrict outside IP address traffic in VNet you must configure Azure Firewall.

If you want to restrict traffic within VNet then you must configure Network Security Group in subnet. Suppose within your VNet you created 2 Subnet. One subnet called as subnet-web for Web Apps. Which are exposed to public IP address. So that people can access your app. Then in this subnet you need different rule.

You created another subnet-business where you deploy resources containing your business rules.

You created another subnet-data where you deploy resources containing your databases.

Now you want to restrict that any resources in subnet-web can not communicate directly to subnet-data resources. You need to create Network Security Group (NSG) in order to achieve this security.

However, you want to restrict both subnet-data and subnet-business resources from outside world even from VPN clients. You have to setup Azure Firewall which works at VNet level. There you can create rule that outside traffic can not directly go to subnet-data or subnet-business.

Why do I create Subnets in Azure, how it help securing resources?

I categorize Azure resources in 3 divisions:

  • Public/Internet exposed resources
  • Internal business resources
  • Private resources

In order to secure private resources over azure. We should restrict outside IP addresses to communicate our private Azure resources like Azure storage, DB, Key Vault etc.

To secure resources in Azure we can use below Azure services:

  • Azure Firewall
  • Network Security Group
  • Application Gateway. (2 and 3 are required when we have multiple subnets. Partitioning resources in various subnets are recommended also.)

For robust security, we must deploy both Azure Firewall and Azure Network Security Group or Azure Application Gateway. I personally prefer Azure Firewall and Application Gateway. Because Application Gateway provides easy and friendly way to manage resources.

In order to separate resources in private and public access category and secure them accordingly we need to create Azure Subnet. We want strong security for our private resources.

We can create 1 Subnet where we put resources which are open for public like public web apps. Like Sample Test Exams which is exposed to public over internet. We can call this subnet as subnet-public

Create another subnet where deploy resources which are only available to internal business users like CORE CMS. We can call this subnet as subnet-internal

Create another subnet which should contain resources that we should keep private, secured from any users and restricted outside IP to access or connect. Those resources could be azure storage, cosmos DB or other databases and azure key vaults etc.. Therefore, we can create another subnet call it subnet-private.

Now, In order to secure subnet-private such that outside IP can not connect, we must deploy NSG or application gateway in subnet-private and configure such that only our subnet-public and subnet-internal resources can communicate to subnet-private.

Securing Azure resources using 3 Tier Architecture

We can also create classic 3-tier architecture in Azure where we create 3 subnets as listed below: 1- subnet-web ( private exposed to some public IP or internet) 2- subnet-business ( private ) 3- subnet-data ( private )

  • Subnet-Web can only communicate with Subnet-Business.
  • Subnet-Business can only communicate with Subnet-Data.
  • Subnet-Business and Subnet-Data are never exposed to any public access.

In subnet-web we deploy resources that can be exposed to internet. Such as web apps. In subnet-business, we deploy resources where only subnet-web can connect to. Example: Function apps, where we write business logic and handlers. In subnet-data, we deploy private resources such as azure storage, cosmos DB or other databases and azure key vaults etc. And only subnet-business can connect to these resources.

This way we can secure our private resources.

If in your Azure, your are putting all resources in single subnet or no subnet just VNet. And exposing to internet via filtering selected IP addresses. Still we are at risk since we exposed all resources over the internet via selected IP. You must think to protect Databases, Keyvaluts etc. and do not allow any public connection by any means.

Securing Azure resources using Azure Firewall

Azure Firewall can filter all perimeter network. You can also put filter such that all the traffic towards your VNet should go through Firewall. If you have hybrid connection then on-premise traffic can also be diverted to go through Azure Firewall.

Your subnets within the Spoke VNet can be configured to use UDR (user defined routes). Where you can put the routing rules. Like subnet-web can not talk to subnet-data etc. Also we need to setup rules that traffic on subnets within spoke VNet should go out through Azure Firewall only.


Thanks for reading my article till end. I hope you learned something special today. If you enjoyed this article then please share to your friends and if you have suggestions or thoughts to share with me then please write in the comment box.

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Rupesh Tiwari
Founder of Fullstack Master