Azure Networking Best Practices

Network Design Principles

A well-designed network is the foundation for a secure, scalable, and performant Azure deployment. Consider the following principles:

1. Hub-and-Spoke Architecture

This is a highly recommended pattern for most Azure deployments. It offers:

Centralized security and firewall management.
Simplified routing and network management.
Reduced complexity in large environments.

In this model, a central "hub" virtual network (VNet) connects to multiple "spoke" VNets. The hub typically contains shared services like firewalls, NAT gateways, and VPN/ExpressRoute gateways.

2. Virtual Network Peering

Use VNet peering to connect VNets within the same region or across regions. This provides high-bandwidth, low-latency connectivity between VNets without requiring a gateway.

Note: Ensure address spaces do not overlap when peering VNets.

3. Address Space Planning

Carefully plan your Azure Virtual Network address spaces. Avoid overlapping address spaces with your on-premises networks or other Azure VNets that will need to communicate.

Use private IP address ranges (RFC 1918).
Allocate sufficient space for future growth.
Consider using a consistent CIDR block strategy.

4. Subnetting Strategy

Divide your VNets into subnets based on function, security, or application tier. This aids in granular network security policy application.

Smaller subnets for specific workloads.
Dedicated subnets for services like Azure Bastion, Kubernetes, etc.
Reserve space within subnets for future expansion.

Security Best Practices

Securing your Azure network is paramount. Implement a defense-in-depth strategy.

1. Network Security Groups (NSGs)

NSGs act as a basic firewall at the network interface or subnet level. Apply least privilege principles to NSG rules.

Deny all inbound and outbound traffic by default.
Allow only necessary traffic.
Use service tags to simplify rule management (e.g., AzureLoadBalancer, Internet).

                
# Example NSG rule to allow SSH from a specific IP range
{
    "properties": {
        "priority": 100,
        "protocol": "*",
        "access": "Allow",
        "direction": "Inbound",
        "sourceAddressPrefix": "203.0.113.0/24",
        "sourcePortRange": "*",
        "destinationAddressPrefix": "*",
        "destinationPortRange": "22",
        "name": "AllowSSHFromTrusted"
    }
}
                
            

2. Azure Firewall

For more advanced threat protection, use Azure Firewall. Deploy it in your hub VNet.

Centralized network policy enforcement.
Threat intelligence-based filtering.
Network and application FQDN filtering.
TLS inspection.

3. Azure DDoS Protection

Azure DDoS Protection Standard provides enhanced DDoS mitigation capabilities for your Azure resources.

Adaptive tuning and alerting.
Attack analytics and reporting.
SLA guarantees.

4. Private Endpoints and Service Endpoints

Securely connect to Azure PaaS services without exposing them to the public internet.

Private Endpoints: Provide a private IP address from your VNet to an Azure service.
Service Endpoints: Extend VNet identity and direct connectivity to specific Azure services over the Azure backbone.

5. Network Virtual Appliances (NVAs)

For specialized security functions (e.g., advanced intrusion detection/prevention), consider deploying NVAs from Azure Marketplace.

Performance Optimization

Ensure your network can handle your application's traffic demands.

1. Azure Load Balancer

Distribute network traffic across multiple VMs or services using Azure Load Balancer for high availability and performance.

Layer 4 load balancing.
Health probes to detect unhealthy instances.
Support for internal and public IP addresses.

2. Azure Application Gateway

For Layer 7 load balancing, use Application Gateway. It offers features like SSL termination, cookie-based session affinity, and Web Application Firewall (WAF).

3. Bandwidth and Throughput

Monitor network throughput and bandwidth utilization. For high-demand scenarios:

Choose appropriate VM sizes with adequate network bandwidth.
Consider Azure Accelerated Networking.
Optimize application communication patterns.

4. ExpressRoute and VPN Gateway Performance

If connecting to on-premises, ensure your ExpressRoute circuits or VPN Gateway SKUs meet your performance requirements.

Management and Monitoring

Effective monitoring and management are key to maintaining a healthy network.

1. Azure Monitor

Leverage Azure Monitor to collect, analyze, and act on telemetry from your Azure network resources.

Network Watcher: A suite of tools for monitoring, diagnosing, and viewing metrics of your Azure network.
Connection Monitor: Troubleshoot network latency and packet loss.
IP Flow Verify: Diagnose NSG rules blocking traffic.
Topology: Visualize network resources and their dependencies.

2. Traffic Analytics

Analyze network traffic flow logs from Azure Firewall and NSGs to gain insights into traffic patterns and identify potential security threats.

3. Logging and Auditing

Enable diagnostic logs for all critical network services (e.g., Azure Firewall, Load Balancer, Application Gateway) and send them to a Log Analytics workspace or storage account for auditing and troubleshooting.

4. Tagging Strategy

Implement a consistent tagging strategy for all network resources. This aids in cost management, organization, and automation.

Governance and Compliance

Enforce policies and standards across your Azure network.

1. Azure Policy

Use Azure Policy to enforce organizational standards and assess compliance at scale.

Restrict regions where VNets can be deployed.
Enforce specific NSG rule configurations.
Ensure Azure Firewall is deployed for specific VNets.

2. Resource Locks

Apply read-only or delete locks to critical network resources to prevent accidental deletion or modification.

3. Compliance Requirements

Ensure your network design and configuration meet any regulatory or industry compliance standards (e.g., GDPR, HIPAA, PCI DSS).

Continuous Improvement

Networking in the cloud is dynamic. Regularly review your network architecture, security posture, and performance metrics. Stay updated with new Azure networking services and features to ensure your environment remains optimized and secure.