Multi-Layer Switch

What is a multi-layer switch? We've heard about and used plenty of Layer 2 switches in computer networks all over the world but now we're starting to hear the term "multi-layer” switch and this may be somewhat confusing when you first hear the term. So let's first look once more at what a Layer 2 switch does and its functions. 

Fig 1: Multi-Layer Switch

Coming up! So what is a multi-layer switch? We know that a Layer 2 switch performs fast switch functions of forwarding and separating traffic based on its configuration settings (again, those given to it by you as the admin, technician or engineer) and it forwards that traffic using ASICs (Application Specific Integrated Circuits) which are hardware integrated chip circuits that are really efficient at forwarding and doing the job a switch needs to do on a network. When we hear the term "Layer" in front of a number on a switch 99 percent of the time (in fact most of the time) it's referring to the layer in the OSI Model that it handles and deals with. So a Layer 2 switch deals with the Data Link Layer of the OSI Model Layer 2 and it forwards traffic again using the ASIC hardware. It forwards traffic based on Destination and Source MAC addresses in each frame received from the rest of the network. Now different technology building companies that build network hardware and software components have begun developing multi-layer switches for use. This leads us to the Layer 3 switch. 

Now a Layer 3 switch still uses fast switching with ASICs but it can also perform similar routing functions similar to an actual router. This is important because on many Layer 3 switches in networks and environments where they can be used they can perform a Layer 3 routing function or functions much faster than an actual router because a router uses software to route traffic. The biggest differences between a Layer 3 switch and a router is that a Layer 3 switch uses hardware to forward and route traffic with those ASIC chips and a router uses software. A Layer 3 switch can often contain more physical ports for connectivity of cables and or devices than a router can and a layer 3 switch in most cases is unable to route between different types of cables whereas an actual router can more often route between different types of cables or connections. On a Layer 2 or Layer 3 switch, you typically have to have all or most connections to it running using Ethernet. But a router can actually route and connect between Ethernet and other types of technologies and protocols. 

So those are the primary differences between Layer 2 Layer 3 switches and routers. But Layer can actually load balance by sending traffic to one or many servers that perform the same function for replication, and there's now actually a Layer 7 switch that can read and route traffic based on Layer 7 or the application layer traffic (things like FTP, HTTP, etc.) Also you'll see more of these on the market but there's a Layer 4-7 switch that can or sometimes they just call it a 4 7 switch that can load balance between multiple servers and look at application layer data. Also so some are all of these may be required for you to know on the Network+ exam. But it's really a good idea to know them anyway because as technology advances you'll see more and more of these multi-layer switches being used in more and more networks around the planet.