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Layer 4 switch

Layer 4 switch

(also transport layer switch, L4 switch)

Layer 4 switch definition

A layer 4 switch functions at the transport layer (layer 4) within the OSI model, empowering it to determine routing based on information from both the network layer (layer 3) and the transport layer (layer 4). As a result, layer 4 switches can provide sophisticated capabilities like load balancing, traffic prioritization, and quality of service (QoS) by considering application and protocol specifics.

See also: packet capture, OSI layer, cyberattack

Layer 4 switch examples

  • Load balancing: Layer 4 switches can distribute network traffic evenly across multiple servers, optimizing resource utilization and reducing latency.
  • Packet prioritization: Layer 4 switches can prioritize certain types of traffic, like voice over IP (VoIP) or video streaming, to ensure a smooth user experience.
  • Quality of Service (QoS): Layer 4 switches can allocate bandwidth based on the type of application, protocol, or user, ensuring that critical applications and services receive the resources they need.

Layer 4 switch vs. layer 3 switch

While layer 3 switches operate at the network layer and make routing decisions based on IP addresses, layer 4 switches operate at the transport layer and consider additional information like port numbers and application protocols. This enables layer 4 switches to provide more advanced features, such as load balancing and QoS, compared to layer 3 switches.

Pros and cons of layer 4 switches


  • Advanced features like load balancing and QoS.
  • Packet prioritization for a better user experience.
  • Optimized resource utilization and reduced latency.


  • Higher cost compared to layer 3 switches.
  • Increased complexity in configuration and management.

Tips for using layer 4 switches

  • Deploy layer 4 switches in environments that require advanced features, such as data centers or large enterprises.
  • Use layer 4 switches to optimize network performance for latency-sensitive applications like VoIP or video streaming.
  • Consider the cost-benefit analysis before implementing layer 4 switches, as they may be more expensive and complex than layer 3 switches.

Further reading

Ultimate digital security