VNets

VNets, short for virtual networks, are a foundational construct in Microsoft Azure that provide isolated, private network boundaries for cloud resources. A VNet enables resources such as virtual machines, databases, and apps to communicate securely while offering control over IP addressing, DNS, and security policies. VNets are defined by an address space and can host multiple subnets, allowing workload segmentation and isolation between environments.

An Azure VNet is defined by an address space expressed as one or more IPv4 CIDR blocks. Within the address space, subnets allocate smaller ranges to individual resources. Each resource attaches to a network interface with a private IP address; optional public IPs enable Internet connectivity. DNS can use the Azure-provided service or custom resolvers. Security is enforced with Network Security Groups that filter traffic and with route tables that control traffic flow between subnets or toward gateways.

Connectivity and hybrid options include VNet peering, which connects VNets to enable seamless cross-network communication with low latency. For on-premises connectivity, a VNet can connect through a VPN gateway (IPsec) or via ExpressRoute for private, direct connections. Azure also supports Private Link and Private Endpoints to access Azure services over a private IP within a VNet, enhancing security and reducing exposure to the public Internet.

Management and deployment are performed through the Azure portal, the Azure CLI, PowerShell, or infrastructure-as-code tools such as ARM templates and Bicep. VNets are commonly used to host and isolate multi-tier applications, support scalable development and testing environments, and enable hybrid cloud architectures, while requiring careful address-space planning and security configuration.