What is a network switch?
A network switch (also known as a switching hub, a bridging hub, or a MAC bridge by the IEEE) is a piece of networking hardware that connects devices on a computer network by employing packet switching to accept and forward data to the destination device.
A network switch is a multiport network bridge that employs MAC addresses to forward data at the OSI model’s data link layer (layer 2). By implementing routing capability, certain switches can also forward data at the network layer (layer 3). Layer-3 switches or multilayer switches are popular names for such switches.
How does the network switch works?
When a device is attached to a switch, the switch records its media access control (MAC) address, which is a code embedded in the network interface card (NIC). The NIC is connected to an Ethernet wire, which connects to the switch. The MAC address is used by the switch to determine which device is sending outgoing packets and where to deliver incoming packets.
The MAC address identifies the physical device and does not change; however, the network layer (Layer 3) IP address can be dynamically allocated to a device and can vary over time. (Think of a MAC address as a car’s VIN number, and an IP address as the registration plate.)
When a packet enters the switch, it examines its header, compares it to the destination address or addresses, and then sends the packet out through the relevant ports that lead to the destination devices.
Most switches include full-duplex functionality, which allows packets arriving from and going to a device to access the full bandwidth of the switch connection, to limit the possibility of collisions between network traffic traveling to and from a switch and a connected device at the same time. (Imagine two people conversing on smartphones rather than a walkie-talkie.)
While switches operate at Layer 2, they can also operate at Layer 3, which is required to support virtual LANs (VLANs), which are logical network segments that can cross subnets. Traffic must flow across switches to get from one subnet to another, which is helped by routing capabilities built into the switches.
What is the difference between a switch and a router?
Routers determine paths for data packets to cross networks and reach their destinations. Routers do this by connecting with multiple networks and transmitting data from the network to the network — including LANs, wide area networks (WANs), or autonomous systems, which are the enormous networks that make up the Internet.
In practice, this means that routers are required for an Internet connection, whereas switches are solely needed to link devices. Routers are required for Internet connection in homes and small offices, although most do not require a network switch unless they require a high number of Ethernet ports. Large offices, networks, and data centers with dozens or hundreds of computers, on the other hand, frequently require switches.
What is a layer 2 and layer 3 switches?
Network switches can operate at either OSI layer 2 (the data connection layer) or layer 3 (the transport layer) (the network layer). Layer 2 switches route data based on the destination MAC address (definition below), whereas layer 3 switches route data based on the destination IP address. Some switches can perform both functions.
The majority of switches, however, are layer 2 switches. Ethernet cables are most commonly used to connect Layer 2 switches to the devices in their networks. Ethernet cables are physical connections that connect to devices via Ethernet ports.
What are the purposes of a network switch?
The following are the primary purposes or functions of switches:
Connect multiple hosts: A switch typically provides a large number of ports for cable connections, enabling star topology routing. It is typically used to link numerous computers to a network.
Forwards a message to a given host: A switch, like a bridge, employs the same forwarding or filtering logic on all ports. When a host on the network or a switch delivers a message to another host on the same network or switch, the switch receives and decodes the frames to read the message’s physical (MAC) address.
Control traffic: A switch in networking may easily link devices such as PCs and access points and regulate traffic entering and exiting the network.
Maintain a clean electrical signal: When a switch forwards a frame, an undistorted square electrical signal is generated.
Increase LAN bandwidth: A switch divides a LAN into many collision areas with independent broadband, allowing the LAN’s bandwidth to be considerably increased.
Applications of Network Switch
Switches are used practically everywhere nowadays, from small offices/home offices (SOHO) to huge ISPs (Internet Service Providers). You can put them in your home office or a small location if you want. A 10/100/1000BASE-T Gigabit Ethernet switch is sufficient for these locations. Furthermore, many switches have high-speed uplink connections that can provide speeds of 10 Gbps, 40 Gbps, or even 100 Gbps! These high-speed switches are often used by businesses when building data centers. In such cases, a 10GbE switch or a 40/100G switch may be required.