Networking does not work without the physical and virtual devices that make up the network infrastructure.
Network architecture varies based on size, network topology, workloads, and business requirements, among other factors. For example, a corporate network may require hundreds or thousands of different network devices to support and expand its data center, LAN, and WAN. In contrast, a simple home network may only need two devices.
Below are eight common types of network devices, with the exception of load balancers and firewalls, which are commonly found in networks.
1. Access point
An access point (AP) is a device that sends and receives data wirelessly over radio frequencies, using the 2.4 GHz or 5 GHz bands. Clients, such as laptops or cell phones, connect to an access point using a wireless signal, allowing them to join the wireless LAN created by the access point . An Ethernet cable physically connects the access point to a router or switch in a wired LAN, allowing the access point to access the Internet and the rest of the network.
When deploying access points, wireless teams must consider factors such as location, attenuation, and channel interference, all of which can affect signal strength. Typically, engineers mount access points on ceilings or walls to maximize signal coverage and minimize potential obstructions.
Access points operate at layer 2 of the OSI model, the data link layer.
A network bridge acts as an interconnection between two or more LANs, essentially creating a single domain from separate LANs. In this way, a bridge is different from a router, which allows communication between different networks but treats them as discrete systems.
A bridge groups partitioned network segments together and controls the traffic that moves between them. A transparent bridge interconnects LANs that use the same protocol suite, while a translation bridge connects LANs that use different protocols.
Bridge devices have switching capabilities, with which they forward incoming data frames by examining media access control (MAC) addresses. With each frame it receives, a bridge builds a lookup table of MAC addresses and port locations. The bridge refers to this table to determine whether to forward a frame or discard it, which occurs when a MAC address is not in the bridge’s domain.
Bridges are no longer commonly used in enterprise network designs and are generally replaced by switches.
A bridge operates at layer 2 of the OSI model.
A gateway is a network node that connects discrete networks or systems that use different protocols, allowing data to flow between networks. Gateways use multiple protocols and translate the information and protocol of an incoming packet to make it compatible with the destination environment. After a gateway processes the data packet, it typically forwards it to a router, which sends the packet to its destination within the network.
Types of gateways include routers, web application firewalls, and email security gateways. Gateways are also frequently used in IoT and cloud environments.
Gateways can operate at any layer of the OSI model.
A hub is a physical device used to join multiple devices on the same LAN. For example, a laptop, desktop, and printer can connect to hub ports with Ethernet cables and be part of the same local network. Unlike a bridge, router, or switch, a hub broadcasts the messages it receives from one port to all remaining ports without examining the frames or isolating the message for the intended destination.
A hub must connect to a router or switch in order to communicate outside of its local network. Hub devices can also connect to each other to extend the global network.
A hub can be active, passive, or smart. Active hubs act as repeaters to amplify or repair the signal of an incoming message before broadcasting it to the rest of the ports. Passive hubs do not amplify message signals, merely providing connectivity for devices on its ports. Smart hubs have management and monitoring capabilities to identify potential issues with connected devices.
A hub operates at layer 1 of the OSI model, the physical layer.
The main purpose of a modem is to modulate and demodulate – or convert – signals between devices, such as analog to digital. The most common type of modem today is an Internet modem, which facilitates Internet access by receiving signals from an ISP and converting them into a format that connected devices can use, such as radio signals or digital.
A modem typically connects to a router, which receives Internet access from the modem and sends it to other devices on the network. Modems can use Ethernet, DSL, fiber, or wireless cable for connectivity. ISPs frequently provide modems that have combined routing and firewall capabilities.
Depending on the type, a modem operates at Layer 1 or Layer 2 of the OSI model.
A repeater reinforces a signal and sends it back to its destination. Repeaters are used to combat attenuation, circumvent interference, and extend the range of a signal. They are commonly used in wireless networks, but also work with fiber optics, telephones, and television broadcasting, among others.
While a hub amplifies signals from multiple devices connected to its ports, a simple repeater has only two ports – one for incoming signals and one for outgoing signals.
A repeater operates at layer 1 of the OSI model.
A router directs data requests from one network to another. Routers examine incoming packets to determine the appropriate destination IP address, then forward the packet to that destination. A router can also provide access to the Internet through its connection to a modem or as a combined modem-router.
As with a bridge, routers maintain and use routing tables that contain routing information, such as IP addresses and interfaces. Once a router inspects a packet, it refers to the routing table to find the best path to the destination. Routers use routing protocols to communicate and exchange data.
Types of routers commonly used in corporate networks are:
- edge routers
- main routers
- distribution routers
- wireless routers
A router operates at layer 3 of the OSI model – the network layer.
A network switch transmits data to its destination by examining the MAC address of an incoming frame and sending it to the device with the corresponding address.
Devices connect to ports on a switch typically via an Ethernet cable. The switch stores the MAC addresses of these devices in an address table that it uses as a reference when forwarding frames. While a router forwards the data to an IP address or network, a switch sends the information directly to the specific destination port.
Unlike a hub, which shares bandwidth among all of its ports, a switch allocates bandwidth for each port. Switches are also smarter than hubs because they examine the MAC address of an incoming frame.
Switches are available in the following types:
- unmanaged switches
- managed switches
- smart switches
- Layer 2 switches
- Layer 3 switches
- Power over Ethernet Switches
- fixed switches
- stackable switches
- modular switches
A traditional switch operates at layer 2 of the OSI model. Layer 3 switches operate at the network layer and forward packets based on the destination IP address.