IP Encyclopedia > Switch

What Is a Switch?

A switch enables network communication for connected IT devices. Switches fall into different categories from different perspectives, including Ethernet switches, Layer 3 switches, campus switches, data center switches, core switches, aggregation switches, access switches, fixed switches, and modular switches.

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What Is a Switch Used for?

The main purpose of a switch is to forward data and implement communication and interconnection between network devices. The functions are described as follows:

Segments a network into multiple isolated local area networks (LANs) or virtual local area networks (VLANs) to improve network security.
Identifies received data and accurately forwards the data to intended destination devices to improve network performance.
Controls and manages traffic on different ports and from different users and applications to optimize the network environment and improve network reliability and stability.
Optimizes the data transmission method to improve transmission efficiency.

In addition to the preceding basic functions, switches provide more functions, such as link aggregation and even firewall functions.

How Does a Switch Work?

A switch forwards a data packet based on the physical address (MAC address). For the IP protocol, the switch is transparent. That is, when forwarding a data packet, the switch does not and needs not know the IP address of the source or destination machine. It only needs to know the destination MAC address.

When a switch is working, it continuously collects information to create a MAC address table. This table simply indicates the mapping between a port on which a data frame is received and the MAC address from which the data frame is received.

When receiving a TCP/IP packet, the switch checks whether the packet is a broadcast packet. If so, the switch broadcasts the packet out of all ports. Otherwise, the switch checks its MAC address table to see if it already has an entry for the destination MAC address. If a matching entry is found, the switch forwards the packet through the corresponding port. If the destination MAC address is the same as the source MAC address, the switch considers the packet invalid and discards it.

If no matching entry is found in the MAC address table, the switch sends the packet out of all ports except the port on which it is received. This process is similar to broadcast. After the reply from the destination is received on a port, the switch learns the new MAC address to port association and adds it to the MAC address table.

Working mechanism of a switch

Classification of Switches

Switches can be classified into different types based on application scenarios, network layers, and management types.

Table 1-1 Classification of switches

Classification Criteria	Switch Type	Characteristics
Application scenario	Campus switch	Builds campus networks that feature simplified management, high stability and reliability, and intelligent services for various sectors, such as enterprises, public services, education, finance, and manufacturing.
Application scenario	Data center switch	Is designed for cloud data centers and high-end campus networks and applicable to various scenarios and network scales, featuring large-scale deployment, automation, programmability, and real-time visibility.
Network layer	Access switch	A switch working at the access layer, which is inexpensive and has a high port density, suitable for directly connecting IT devices and networks.
	Aggregation switch	A switch working at the aggregation layer as an aggregation point of multiple access switches, with a higher performance and switching speed than access switches.
	Core switch	A switch working at the core layer that must meet the demanding requirements for reliability, performance, and throughput.
Management type	Unmanaged switch	A basic switch with no web or Simple Network Management Protocol (SNMP) management option. It is plug-and-play and does not involve user login or configurations such as commissioning.
	Web-managed switch	A switch whose functions can be simply and visually managed with a web GUI.
	Fully-managed switch	A switch that supports various management and maintenance methods, such as SNMP, web, command line interface (CLI), and provides a user-friendly configuration interface.
OSI model	Layer 2 switch	A switch that works at Layer 2 (data link layer) of the OSI model and can identify MAC addresses in data frames. A Layer 2 switch is also known as an Ethernet switch.
OSI model	Layer 3 switch	A switch that works at Layer 3 (network layer) of the OSI model and provides the routing function. It is widely used in large-scale LANs such as school campus networks to accelerate internal data exchange and forwarding.
Port rate	FE switch	A switch whose downlink ports can reach a transmission rate of 100 Mbit/s.
	GE switch	A switch whose downlink ports can reach a transmission rate of 1000 Mbit/s.
	10GE switch	A switch whose downlink ports can reach a transmission rate of 10 Gbit/s.
	Multi-GE switch	A switch whose downlink ports can transmit data at a rate of 100 Mbit/s, 1 Gbit/s, 2.5 Gbit/s, 5 Gbit/s, or 10 Gbit/s.
Device structure	Fixed switch	A switch with an integrated design and a fixed number of ports and functions for easy maintenance and management. A fixed switch is small and can be installed on a desk, on a wall, or in a cabinet.
Device structure	Modular switch	A switch with functionally independent modules and plug-and-play boards, power modules, and fan modules for easy replacement and scalability. A modular switch is large and must be installed in a cabinet.

Switch vs. Router

A router connects two or more networks. When receiving data, the router finds the shortest path to the destination IP address according to the routing table, and then forwards the data to the next-hop address.

Both routers and switches can transmit and forward data on a network, but they differ as follows:

A switch is mainly used for data switching, and a router is mainly used for routing and forwarding.
A switch forwards data based on MAC addresses, whereas a router forwards data based on IP addresses.
A router can select an optimal path from multiple paths to improve the data transmission rate.

Switch vs. Hub

A hub is a device that connects multiple Ethernet twisted pair cables or optical fiber cables to the same physical medium. A hub has multiple I/O ports. When receiving signals from any port, the hub regenerates or amplifies the signals and forwards them to all other ports.

The hub cannot store data and must forward the data immediately after receiving it. Therefore, collision detection is required during data forwarding to prevent data loss caused by collision. Therefore, hubs can work only in half-duplex mode.

In the early stage of networking, the emergence of the hub brought great convenience to people, and were widely used before the invention of the switch. In a sense, the hub is merely a primitive predecessor to the switch. Therefore, hubs were replaced by switches a long time ago. Meanwhile, switches are continuously expanding their functions, and many more advanced and powerful switches are developed to meet different requirements.

What Switches Does Huawei Offer?

Depending on the application scenario, Huawei switches are classified into multiple types. The main two types are campus switches and data center switches.

Huawei Campus Switch

Huawei campus switches are designed to build a campus network that features simplified management, high stability and reliability, and intelligent services.

The benefits of Huawei campus switches include:

Higher reliability: Achieve non-blocking switching and zero packet loss in high-concurrency, heavy-load environments by leveraging fully-programmable chipsets and innovative cell switching technology.
Easier management: Realize wired and wireless convergence from the access layer to the core layer, manage up to 10,240 APs with a single switch, and achieve simplified O&M with unified user authentication.
More agile deployment: Implement plug-and-play onboarding across the network, achieve network deployment and adjustment within minutes, and respond to service changes with greater agility using Software-Defined Networking (SDN) and Virtual Extensible LAN (VXLAN) technologies.

Huawei campus switches come in a variety of models. For details, see Huawei Campus Switch Portfolio. The following figure shows the CloudEngine S8700 series campus switches.

CloudEngine S8700 series campus switches

Huawei Data Center Switch

Data centers are evolving from the cloud era to the intelligence era to power nascent technologies such as 5G and AI. That's why Huawei has launched CloudEngine data center switches. These switches feature 400GE ultra-broadband, lossless Ethernet, and full-lifecycle automated management, revitalizing the digital transformation of our customers.

The benefits of Huawei data center switches include:

High scalability and flexibility: The diversified product portfolio supports flexible networking consisting of 500 to over 50,000 servers, and the real-time analysis on collected data enables quick service innovation and intelligent O&M.
Automation and agility: iMaster NCE-Fabric automatically manages overlay and underlay networks by integrating with third-party DevOps tools through standard open APIs.
Open architecture for smooth evolution: The unified open architecture facilitates the smooth evolution of conventional data center networks to embrace the SDN and multi-cloud technologies.

Like campus switches, Huawei data center switches also come in an array of models. For details, see Huawei Data Center Switch Portfolio.

CloudEngine XH16800 series switches are core data center switches designed for AI scenarios, featuring high efficiency and availability. In terms of computing efficiency, CloudEngine XH16800 series switches support network-level load balancing (NSLB), improving training efficiency by 20%. In terms of computing availability, CCAE integrated O&M is supported, improving troubleshooting efficiency by 90%.