Introduction

In the current cloud-centric era, grasping how resources within Azure Virtual Networks (VNet) access the internet is indispensable for architects and IT professionals. This comprehensive article delves into the various mechanisms available for Azure resources to access the internet, highlighting the configurations, benefits, and considerations of each, enriched with best practices, insightful tips, and practical examples.

Background: Virtual Network and Internet Access

Every Azure VNet represents an isolated segment of the Azure cloud, defined by a specific IP address space. Within this VNet, multiple subnets are allocated, each with its distinct IP range. Resources, like virtual machines (VMs), are assigned private IP addresses within these subnets.

Protect Your Data with BDRSuite

Cost-Effective Backup Solution for VMs, Servers, Endpoints, Cloud VMs & SaaS applications. Supports On-Premise, Remote, Hybrid and Cloud Backup, including Disaster Recovery, Ransomware Defense & more!

The crucial point is that even if an internet-routable IP address range is utilized within a VNet, it’s treated as a private IP and remains inaccessible directly from the internet. A translation to a public IP address is pivotal for these resources to access the internet.

Explicit Internet Access Mechanisms

As Azure transitions towards a more secure and controlled approach for internet access from VMs, effective 30 September 2025, the default outbound access for VMs will be retired.
This mandates explicit outbound connectivity methods for new VMs requiring internet access. Here’s a deeper dive into the available mechanisms:

Instance-Level Public IP

  • Description: Assigning a public IP address directly to a VM is the most straightforward method
  • Best Practice: Use this method judiciously as it can expose a broader surface area for potential cyber-attacks
  • Example: Ideal for specific scenarios like a public-facing web server, though not a scalable solution for larger deployments

External Standard Load Balancer

  • Description: Azure’s external standard load balancer distributes incoming traffic among backend VMs and, through outbound rules, enables internet access for VMs
  • Best Practice: Separate inbound and outbound traffic by utilizing different public IPs to enhance security and manageability
  • Tip: Configuring health probes ensures only healthy VMs receive traffic, improving overall application responsiveness

NAT Gateway

  • Description: The Azure NAT Gateway is purpose-built for enabling internet connectivity, supporting up to 16 public IPs and an impressive 64,512 ports per IP
  • Best Practice: Assign the NAT Gateway to specific subnets to control how resources access the internet, enhancing security and manageability
  • Example: Ideal for scenarios requiring robust egress connectivity without exposing internal resources

Azure Firewall

  • Description: Azure Firewall, a stateful firewall-as-a-service offering, provides granular control over network traffic
  • Best Practice: Integrate with NAT Gateway for a layered approach to network security
  • Tip: Utilize Azure Firewall’s threat intelligence-based filtering for enhanced security

Implicit Public IP Allocation

With the retirement of default outbound access post-September 2025, the reliance on implicit public IP allocation for internet access expires for new VM deployments. This identifies the importance of establishing explicit internet access mechanisms for seamless connectivity.

Download Banner

Important Considerations

Symmetric Routing

  • Description: Ensuring that requests and responses traverse the same path is crucial for network stability
  • Tip: Utilize Azure’s built-in routing tables or customize your own to ensure symmetric routing, preventing potential connectivity issues

Zone Redundancy

  • Description: Some services like Azure Firewall offer zone-redundant options, while others like NAT Gateway do not
  • Best Practice: Plan for high availability by deploying resources across multiple zones, minimizing cross-zone dependencies

Transition to Explicit Outbound Connectivity

  • Description: The forthcoming policy change emphasizes the need to plan for explicit outbound connectivity methods
  • Example: Transitioning to Azure NAT Gateway or Azure Load Balancer outbound rules well before the policy change date to ensure uninterrupted internet access

Additional Tips and Tricks:

  • Network Security Groups (NSGs): Utilize NSGs to control inbound and outbound traffic to network interfaces, VMs, and subnets
  • Azure Policy: Employ Azure Policy to enforce organizational requirements and ensure network configurations adhere to best practices
  • Monitoring and Diagnostics: Leverage Azure’s robust monitoring and diagnostic tools like Azure Monitor and Network Watcher to gain insights into your network performance and security

Conclusion

Azure’s ever-evolving ecosystem continues to offer many options for resources within VNets to access the internet. The retirement of default outbound access reiterates the importance of understanding and implementing explicit outbound connectivity methods to balance accessibility, scalability, and security.

Using best practices, leveraging tips and tricks, and learning through practical examples significantly empower IT professionals in navigating the Azure ecosystem.

Staying updated with these configurations and best practices is instrumental for any IT professional working in the Azure ecosystem, ensuring their network infrastructures are adeptly prepared for future advancements, resulting in a secure and efficient cloud networking environment.

Read More:
Microsoft Azure for Beginners: Azure Update Manager Explained: Part 27

Follow our Twitter and Facebook feeds for new releases, updates, insightful posts and more.

5/5 - (1 vote)