What is the purpose of Azure Load Balancer?
Azure Load Balancer operates at Layer 4 and uses rules and health probes to distribute TCP and UDP traffic evenly across a backend pool of virtual machines or instances. By sending traffic only to healthy backend resources, it improves availability and enables scaling by adding more instances without changing the front-end IP. This precisely matches the described purpose of distributing incoming network traffic across multiple backend resources.
Why this answer
Azure Load Balancer operates at Layer 4 (TCP/UDP) of the OSI model to distribute incoming traffic across healthy backend resources, such as virtual machines or instances in a backend pool. It uses a hash-based distribution algorithm (5-tuple hash for inbound traffic) to ensure high availability and scalability by spreading requests evenly. This directly supports fault tolerance by automatically routing traffic away from unhealthy instances based on health probes.
How to eliminate wrong answers
Option A is wrong because caching web content at edge locations globally is the purpose of Azure Content Delivery Network (CDN) or Azure Front Door, not Load Balancer. Option C is wrong because connecting on-premises networks to Azure is achieved via Azure VPN Gateway or Azure ExpressRoute, which provide site-to-site or dedicated private connectivity. Option D is wrong because managing domain names and DNS routing is the function of Azure DNS or Azure Traffic Manager, which handle name resolution and traffic routing based on DNS policies, not Layer 4 load balancing.