L3-4 SLB

Layer 3-4 Server Load Balancing (L3-4 SLB) is a foundational technology that manages the distribution of incoming network traffic among multiple servers based on IP addresses and TCP/UDP ports. By operating at the network and transport layers of the OSI model, L3-4 SLB ensures that no single server becomes a bottleneck, improving application responsiveness and reliability.

Commonly used in data centers, cloud environments, and enterprise networks, L3-4 SLB supports high-throughput, scalable services by balancing client requests according to algorithms such as round-robin, least connections, or hash-based methods. Health monitoring features allow the load balancer to detect server failures and reroute traffic to healthy nodes, enhancing service availability and business continuity.

Unlike application-layer (L7) load balancers, L3-4 SLB does not inspect packet payloads, making it efficient for a wide range of protocols and applications. However, it offers basic security features such as IP filtering and can mitigate simple denial-of-service attacks by distributing load and isolating unhealthy traffic patterns. For advanced traffic management and application-aware policies, L3-4 SLB is often complemented by L7 load balancing solutions.