Business networks today need to use switches to connect computers, printers and servers within a building or campus.
A network switch is a small hardware device that centralizes communications among multiple connected devices in one local area network (LAN).
In short, a network switch usually serves as a controller, enabling networked devices to talk to each other efficiently. Through information sharing and resource allocation, switches save businesses money and increase employee productivity.
There are a few categories of switches today, distinguished by function:
- Unmanaged (Layer 2) switch
- Managed (Layer 2) switch
- Managed Layer 3 switch (multilayer switch)
Unmanaged Layer 2 Switches
A modern unmanaged switch provides the functionality of a multiport bridge; each of the switch ports is on its own collision domain. Like bridges, the switch has built-in support for the Spanning Tree Protocol (STP), which provides loop prevention when multiple switches (bridges) are connected, introducing the potential for switching loops. A switch also keeps an internal database of the known MAC addresses connected to each port. This information is used to reduce the amount of Ethernet frame flooding that occurs when a device location is unknown (as with hubs).
Managed Layer 2 Switches
A modern managed switch provides all the functionality of an unmanaged switch; in addition, it can control and configure the behavior of the device. This typically introduces the ability to support virtual LANs (VLANs), which is why almost all organizations deploy managed switches versus their cheaper alternatives.
Managed Layer 3 Switches (Multilayer Switches)
The final type of switch is a Layer 3 or multilayer switch (MLS). This type of device provides a mix of functionality between that of a managed Layer 2 switch and a router. (The next section describes routers.) The amount of router function overlap is highly dependent on the switch model. At the highest level, a multilayer switch provides better performance for LAN routing than almost any standard router on the market, because these switches are designed to offload a lot of this functionality to hardware.