A network switch is an integral component in most modern networks, providing connectivity between devices within a local area network (LAN). Switches operate at layer 2 (data link layer) of the OSI model and use MAC addresses to forward frames to the correct destination device. But what exactly does a network switch do? Let's break it down.
The key function of a switch is to segment a network for better performance and security. Without a switch, all devices would have to contend for bandwidth on a single shared network segment. A switch creates dedicated collision domains for each port, allowing devices to have full access to the network capacity. This boosts overall throughput.
Switches build MAC address tables by examining the source MAC address of each frame received. This allows the switch to learn which devices are connected to which ports. The table is consulted when forwarding frames - frames are forwarded only to the port associated with the destination MAC address. This eliminates unnecessary broadcast traffic seen on hubs.
A switch also filters frames, only forwarding relevant frames to each device and blocking frames not meant for a particular port. This enhances security and conserves bandwidth. VLANs can further segregate traffic, preventing inter-VLAN communication.
Speed and duplex configuration - Switches allow users to set port speeds and configure full-duplex communication, eliminating collisions.
Port mirroring - Switches can copy traffic from one or multiple ports to another for analysis, increasing network visibility.
Link aggregation - Multiple physical links can be combined into a single logical trunk for added bandwidth between switches or to servers.
QoS and traffic shaping - Quality of service (QoS) mechanisms can prioritize important traffic like voice and video. Traffic shaping prevents congestion and ensures critical traffic gets precedence.
Spanning tree protocol (STP) - STP prevents layer 2 loops in redundant switched networks, providing automatic failover when links fail.
PoE - Power over Ethernet allows switches to pass electrical power along with data on Ethernet cabling to devices like wireless access points or IP phones.
In summary, a network switch is instrumental in dividing a network into smaller broadcast domains. This allows for better throughput by eliminating collisions and unnecessary broadcast traffic. Switches also increase security by filtering traffic based on MAC addresses and offer additional capabilities to improve performance, monitoring, and redundancy. Switches have become essential to any modern high-speed network. When deploying a LAN, switches should be carefully considered to meet the connectivity, performance and scalability needs of your business network.