What should be implemented to restrict inbound traffic to specific IP address ranges?

Network Security Groups (NSGs) are used to filter network traffic to and from Azure resources in an Azure Virtual Network. You can define rules that allow or deny traffic based on IP address, port, and protocol, making them ideal for restricting inbound traffic to specific IP ranges. Availability Sets are used to ensure high availability of virtual machines, not for network security. Azure Firewall is a managed, cloud-based network security service that protects your Azure Virtual Network resources, offering more advanced threat protection than NSGs, but NSGs are the primary and most direct tool for restricting traffic to specific IP ranges at the subnet or NIC level. Azure Monitor collects and analyzes telemetry data from your Azure resources, focusing on monitoring and diagnostics, not traffic filtering.