Virtual Machines Networking
This document provides a comprehensive guide to understanding and configuring networking for Azure Virtual Machines (VMs). Effective networking is crucial for the connectivity, security, and performance of your cloud-based applications.
Introduction to VM Networking
Azure VMs leverage a robust networking infrastructure that allows them to communicate with each other, with the internet, and with your on-premises networks. Key components include Virtual Networks (VNets), subnets, IP addresses, Network Security Groups (NSGs), and more.
Network Interfaces (NICs)
A Network Interface (NIC) connects an Azure VM to a virtual network. A VM can have one or more NICs, allowing for complex networking configurations. Each NIC is assigned a private IP address from the VNet's subnet and can optionally be assigned a public IP address.
Key properties of a NIC:
- IP Configuration: Defines the private and public IP addresses.
- Network Security Groups (NSGs): Applied to control inbound and outbound traffic.
- Application Security Groups (ASGs): Group VMs for easier policy management.
- Accelerated Networking: Enhances network throughput and reduces latency for supported VM sizes.
Virtual Networks (VNets)
An Azure Virtual Network (VNet) is the fundamental building block for your private network in Azure. It provides a logically isolated network for your Azure resources, allowing them to communicate with each other and with the internet.
Features of VNets:
- IP Address Space: Define your own private IP address space.
- Subnets: Segment your VNet into smaller ranges for better organization and control.
- Routing: Control traffic flow within the VNet and to external destinations.
- Connectivity: Connect to on-premises networks via VPN Gateway or ExpressRoute.
Subnetting
Subnetting allows you to divide your VNet's IP address space into smaller, manageable segments. This is essential for security, organization, and routing. Each VM is deployed into a specific subnet.
Best practices for subnetting:
- Plan your IP address allocation carefully.
- Create separate subnets for different tiers of your application (e.g., web, application, database).
- Use Network Security Groups (NSGs) to control traffic between subnets.
IP Addressing
Azure VMs can be assigned private and public IP addresses.
- Private IP Addresses: Assigned from the VNet's address space, used for communication within the VNet and connected networks. Can be static or dynamic.
- Public IP Addresses: Assigned from Azure's public IP address pool, used for communication over the internet. Can be static or dynamic.
A Public IP Prefix is a contiguous range of public IP addresses that you can allocate to your Azure resources.
Network Security Groups (NSGs)
Network Security Groups (NSGs) act as a basic firewall for controlling network traffic to and from Azure resources in an Azure Virtual Network. You can associate an NSG with subnets and/or individual NICs.
NSG rules consist of:
- Priority (lowest number has highest priority)
- Protocol (TCP, UDP, ICMP, Any)
- Source and Destination (IP addresses, IP ranges, service tags, application security groups)
- Port Ranges
- Direction (Inbound/Outbound)
- Action (Allow/Deny)
Security Best Practice: Start with a default "Deny All" rule and explicitly allow only the necessary traffic.
Load Balancing
Azure Load Balancer provides high availability and network load balancing for your applications. It distributes incoming traffic across multiple VMs, ensuring that if one VM fails, traffic is automatically rerouted to healthy VMs.
Types of Load Balancers:
- Standard Load Balancer: Offers enhanced features and is recommended for production workloads.
- Basic Load Balancer: A simpler option for less critical applications.
Azure also offers Application Gateway for Layer 7 (HTTP/HTTPS) load balancing and Azure Front Door for global traffic management.
Azure Firewall
Azure Firewall is a managed, cloud-native network security service that protects your Azure Virtual Network resources. It's a stateful firewall as a service with high availability and cloud scalability.
Key features:
- Network-level filtering
- Application-level filtering (FQDN filtering)
- Threat intelligence-based filtering
- Centralized logging and monitoring
Azure Private Link
Azure Private Link enables you to access Azure PaaS Services (like Azure Storage and SQL Database) and Azure hosted customer-owned/partner services over a private endpoint in your virtual network. Traffic between your virtual network and the service travels the Microsoft backbone network, eliminating exposure to the public internet.
Tip: For secure access to Azure services without public endpoints, always consider using Azure Private Link.