What is a layer-1 switch, layer-2 switch, and layer-3 switch?

Simply put:

Layer-1 switchOnly physical layer protocols are supported (one phone-controlled switch can be called ???)

L2 SwitchSupports physical layer and data link layer protocols, such as Ethernet switches.

L3 SwitchSupports physical layer, data link layer, and network layer protocols, such as some switches with routing functions.

 

 

In terms of the ISO/OSI hierarchy, switches can be divided into L2 switches and L3 switches. A layer-2 Switch refers to the layer-2 data link layer switch that traditionally works in the OSI reference model. Its main functions include physical addressing, error verification, frame sequence, and throttling. A pure second-level solution is the cheapest solution, but it provides minimal control over subnet division and broadcast restrictions. Traditional routers and external switches can also solve this problem, but now the processing speed of the router cannot meet the bandwidth requirements. Therefore, layer-3 switches and Web switches emerged.

A layer-3 switch is a layer-3 Switch with layer-3 routing, it is not simply to overlay the hardware and software of a router device on a LAN switch.

A Web switch provides management, routing, and load balancing transmission for Data Center devices (including Internet servers, firewalls, high-speed buffer servers, and gateways. Unlike traditional network devices, traditional network devices focus on high-speed exchange of individual frames and data packets, while Web switches focus on tracking and processing web sessions. In addition to the connections and packet routing provided by the traditional second/third-layer switches, the Web switch can also provide the complete policies lacking by the traditional LAN switches and routers, it integrates local and global Server Load balancer, access control, service quality assurance (QOS), bandwidth management, and other management capabilities. Currently, Web switches have evolved from purely transport layer (Layer 4) devices to smart Content-based (Layer 7) switches. Using content or user classification for Web Request redirection is a function of the Web server. However, the development of Internet transmission and commerce far exceeds the improvement of computer processing capabilities. Unloading content classification to a Web switch balances the infrastructure of the entire website.

 

 

---------------- Layer 3 switches are switches with routing functions !! The two-layer access is based on the MAC address! -------------------------

 

Currently, there are two common vswitches,

One is a two-layer switch, which is the one we see most. Based on Mac, two-layer fast switching, all interfaces are in the same broadcast domain.

 

The second is the layer-3 switch you mentioned. As the name suggests, a layer-3 switch can use the routing function. In the early stage, a layer-3 Switch needs an msfc (multi-layer switching Feature Card) to support it.Layer-3 routing, The modern layer-3 Switch integrates this function.

Example 1 _ L2 Switch:

Two Layer-2 switches are deployed on the first floor of each floor. VLAN can be divided between them for communication. However, if the switch on the first floor and the switch on the second floor are not in the same VLAN, and they need to communicate with each other, then they need to use the router for routing.

Example 2 _ layer-3 Switch:

If there are more floors and more switches, you only need a three-layer core switch to replace the router.

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The principle of a layer-3 switch is simple: one route is used for multiple exchanges.

Explanation: In the wide area network, of course, layer-3 data packets (routed) are run, and the route needs to determine the optimal path from the source to the destination each time and re-select each time, if you use a layer-3 switch, you can perform the source-to-destination route for the first time. The layer-3 Switch forwards the data to layer-2, or both the source and target are for fast exchange.

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Note:

Vswitches at Layer 2 have the routing function, but cannot completely replace vrouters because their basic principles are different.
In a sense, layer-3 switches are much faster than router policy forwarding!
Layer-3 switches can easily save network resources and prevent congestion.