The term network device covers a lot of ground. Anything from a simple unmanaged switch to a dial-up modem to a UTM (unified threat management) appliance can fit the bill. Additionally, the lines between what category different networking devices fall into can get fuzzy because in many cases a single device performs multiple functions. Show Here, to help you sort through that fuzziness, we tackle the concept of network devices from the ground up. We’ll start with a definition, move into our network devices list, and then discuss some of the important points to consider when managing network devices. What are network devices?Network devices are building blocks that facilitate communication between services and the endpoints that consume those services. In other words, they’re connectors that enable communications between devices on a network. Enabling communication means anything that helps data get from source to destination— a network switch transmitting frames between two devices on a LAN, for example. Restricting communication means stopping that communication from occurring. Examples here include a firewall rule that stops traffic from going to TCP port 23 or a VLAN that breaks up broadcast domains. You’ll notice the word “hardware” is missing from our network devices definition. This is because many network functions and appliances are virtualized or software-based. For example, you can deploy a virtual appliance that acts as a router, network switch, or firewall. OSI model and data types crash courseOne of the best ways to understand the purpose of different network devices is to understand a bit about the layers of the OSI (Open Systems Interconnection) model. The OSI model provides a conceptual model that explains how data flows across and within networks. For understanding how the different network devices work, these two aspects of the OSI model will help:
Here’s a visual representation of the OSI model and the PDUs (data) associated with each layer. 11 types of network device types1. FirewallA firewall is a network security device that monitors and either blocks or allows traffic based on a set of rules. Firewalls can be software, hardware, or a combination of both. Additionally, the rules firewalls use can be based on something straightforward like ports and IP addresses or use heuristics to identify malicious behavior. Common examples of network firewalls include:
2. SwitchThe textbook definition of a network switch is a Layer 2 device that sends and receives frames. These switches are the basic building block of Ethernet networks. Here’s a basic example of how a Layer 2 switch works:
By sending the data to a specific device, the switch is breaking up collision domains and greatly reducing network congestion when compared to network hubs. That breaking up of collision domains is the basic benefit of a Layer 2 switch. However, this basic example of a Layer 2 switch is just one of the many types of network switches. Here’s a list of common types of network switches:
PoE switches: Switches that provide Power over Ethernet (PoE) functionality can provide both network connectivity and power to connected devices. For example, it’s common to power Voice over IP (VoIP) phones using PoE switches. PoE switches can be Layer 2 or Layer 3 switches and can be managed or unmanaged. 3. Access pointOperating at Layer 2, access points (APs)—also known as wireless access points (WAPs)—are the network switches of the wireless world. WAPs connect to a LAN through a wired connection and allow other Wi-Fi devices to communicate. The networks created by WAPs are WLANs (wireless local area networks). At a high level, there are three main types of APs:
4. RouterRouters are the network devices that route packets between networks. These Layer 3 devices enable everything from communication between multiple subnets within the same WAN to the internet connection that allows you to read this article. A good way to think of routers is this: They are the network device that deals with IP addresses. Of course, that definition might leave you wondering why we need routers if we have Layer 3 switches. For some insight on that topic, see Layer 2 vs Layer 3 Network Switches: What’s the Difference? 5. NAS (Network attached storage)A NAS is a server dedicated to file storage. Within a LAN, a NAS provides a central storage point that can be used for things like shared access to files and storing backups of user data. NAS devices generally provide an affordable and simple way to provide network storage. In recent years, the lines between a NAS device and a general-purpose server are getting even more blurred as NASes begin to offer more advanced functionality suited to small and mid-sized environments. 6. Load balancerLoad balancers distribute connections from clients across multiple servers. As with firewalls, there are plenty of software and hardware implementations of load balancers. Load balancers usually operate at Layer 4 (filtering based on TCP or UDP traffic) or Layer 7 (filtering based on HTTP or DNS traffic). Common approaches to load balancing include:
7. RepeaterA repeater is a simple Layer 1 device that rebroadcasts a signal. Repeaters are sometimes referred to as signal boosters. There are repeaters for Wi-Fi, Ethernet, and other network connections, but fundamentally they do the same thing: take a signal in and rebroadcast it.
8. GatewayFrom a hardware perspective, there’s no difference between a gateway and a router. Gateways are simply routers that serve a specific purpose. Gateways are routers that act as the default next hop. When there’s no other route to an IP address on a network, the packets get routed to the network’s default gateway. From there, the default gateway routes the packets on to their next “hop” and the process repeats until the destination is reached. 9. ModemBy the traditional definition, a modem is a device that modulates and demodulates a signal to and from analog and digital. In the days of dial-up internet, modems were used to connect local computer networks to analog telephone lines for internet access. Today, when people say “modem” they may be referring to any number of devices that allow you to connect to a carrier’s network. Examples of popular types of modems include:
10. HubA hub is a simple type of Ethernet repeater that operates at Layer 1, enabling the connection of multiple devices to the same Ethernet network. Unlike a switch, a hub does NOT break up collision domains, meaning all ports on a network hub get sent the same traffic. As a result, hubs—similar to WiFi repeaters—can cause quite a bit of congestion.
11. BridgeTraditionally, network bridges were Layer two devices that often had only two ports. Like switches, they broke up collision domains and could reduce network congestion when compared to hubs by separating the network into multiple collision domains. However, today the term “bridge” can mean a lot more than that traditional definition depending on the context. Other interpretations of the term network bridge:
What about “brouters”? Considering needs for network device managementModern networks include many different types of network devices. Monitoring and managing all of them efficiently can be a difficult task. This is true both when you’re designing a network from the ground up or when you inherit a network someone else designed. Below are some of the key needs to consider when planning your network device management strategy. Network architectureThe infrastructure, devices, services, and topology of your network fall under the umbrella of network architecture. Good network architecture will help you get better overall performance. For example, effective network segmentation can significantly reduce network congestion. Further, by designing for redundancy you can improve network resilience and reduce downtime. Even if you nail your network design and optimization on day one, managing that network long-term can be a real challenge. This is particularly true in large networks where multiple parties were involved in the network design and implementation. Up-to-date and easily accessible network documentation—like network maps, for example—can go a long way in enabling effective network troubleshooting and device management. Of course, there’s a lot that goes into getting network architecture and documentation right and we’ve only scratched the surface here. Network securityNo network device management strategy can overlook network security. If an attacker gains control of your network devices, they’re not really yours anymore. In addition to building security into your network architecture with firewalls, IPS (Intrusion Prevention Systems), and other security appliances, you should take steps to harden your network devices. For example:
Network monitoring toolsThe right network monitoring tools can make a big difference when it comes to network device management. By using protocols like SNMP, syslog, IPMI, and the various flow protocols, network monitoring tools allow you to gain full visibility into your network, create detailed reports on network performance, automate responses to network outages, and monitor all your network devices in real-time. — |