What is a Switch?

A network switch (also called switching hub or bridging hub) is networking hardware device that connects devices on a computer network by using packet switching to receive and forward data to the destination device.

They also operate at the Data Link layer of the OSI model—Layer 2. As it takes in packets being sent by devices that are connected to its physical ports and sends them out again, but only through the ports that lead to the devices the packets are intended to reach. They can also operate at the network layer — Layer 3 where routing occurs.

How Do They Work?

Once a device is connected to a switch, the switch notes its media access control (MAC) address, a code that is integrated into the device’s network-interface card (NIC) that attaches to an ethernet cable that attaches to the switch. The switch uses the MAC address to identify which attached device outgoing packets are being sent from and where to deliver incoming packets.

So, the MAC address identifies the physical device as opposed to the network layer (Layer 3) IP address, which can be assigned dynamically to a device and change over time.

When a device sends a packet to another device, it enters the switch and the switch reads its header to determine what to do with it. It matches the destination address or addresses and sends the packet out through the appropriate ports that leads to the destination devices.

To reduce the chance for collisions between network traffic going to and from a switch and a connected device at the same time, most switches offer full-duplex functionality in which packets coming from and going to a device have access to the full bandwidth of the switch connection.

Bridges and Switches

The first Ethernet bridges were two-port devices that could link two of the original Ethernet system’s coaxial cable segments together. At that time, Ethernet only supported connections to coaxial cables. Later, when twisted-pair Ethernet was developed and switches with many ports became widely available, they were often used as the central connection point, or hub, of Ethernet cabling systems, resulting in the name “switching hub.” Today, in the marketplace, these devices are simply called switches.

Things have changed quite a lot since Ethernet bridges were first developed in the early 1980s. Over the years, computers have become ubiquitous, and many people use multiple devices at their jobs, including their laptops, smartphones, and tablets. Every VoIP telephone and every printer is a computer, and even building management systems and access controls (door locks) are networked. Modern buildings have multiple wireless access points (APs) to provide Wi-Fi services for things like smartphones and tablets, and each of the APs is also connected to a cabled Ethernet system. As a result, modern Ethernet networks may consist of hundreds of switch connections in a building, and thousands of switch connections across a campus network.

Types of Switches

Modular Switches vs. Fixed-Configuration Switches

There are two main categories of switches: modular and fixed configuration. There are variations among these categories of network switches, but the primary definition of each remains the same.

Modular Switches

Modular switches let you add expansion modules as needed, giving you flexibility as network requirements change. Expansion modules are application-specific and include those for firewalls, wireless connectivity, or network analysis. They may also allow for additional interfaces, power supplies, or cooling fans. This type of switch provides you with the most flexibility, but at a higher cost.

Stackable Switches

Stackable switches offer a combination of fixed switch and modular switch. There are some fixed switch models that can be stacked together with other fixed switches of the same model to form a stackable switch unit.

These fixed switches are connected at the back with a special cable therefore can communicate with each other and work as a single switch unit with additional ports. When you manage them, you see all the devices as one switch entity.

Fixed-Configuration Switches

Fixed-configuration switches provide a fixed number of ports and are typically not expandable, which makes them less expensive overall. Fixed-configuration switches include unmanaged switches, smart switches, and managed switches.

See Cisco SG300-52P 52-port Gigabit PoE Managed Switch

Unmanaged Switches

Unmanaged switches are typically used to provide basic connectivity. They are designed to be plug and play; no configuration is needed. Unmanaged switches are most effective when only basic switching and connectivity are required. You will often see them in home networks or wherever only a few ports are needed, such as at a desk, in a lab, or in a conference room.

Some unmanaged switches do offer limited advanced capabilities, however—as the name implies—these switches generally cannot be modified or managed.

Smart Switches

Smart switches offer some management and segmentation, quality of service, and security capabilities, so they can be a cost-effective alternative to modular switches. Still, they are not as scalable as managed switches. These switches are typically deployed at the edge of a large network (while managed switches are used in the core), as the infrastructure for smaller networks, or for low complexity networks.

Managed Switches

Among fixed-configuration switches, managed switches are designed to deliver the most comprehensive set of features to provide the best application experience, the highest levels of security, the most precise control and management of the network, and the greatest scalability. As a result, managed switches are usually deployed as aggregation/access switches in very large networks or as core switches in smaller networks.

Managed switches are the most expensive option of fixed-configuration switches and are most common in organizations with large- or growing- networks.

PoE Switch

PoE Gigabit Ethernet switch is a network switch that utilizes Power over Ethernet technology. When connected with multiple other network devices, PoE switches can support power and data transmission over one network cable at the same time. This greatly simplifies the cabling process. These types of switches in networking provide greater flexibility and you will never have to worry about power outlet when deploying network devices.

Data Center Switches

Data Center switches must support some special characteristics such as very high-speed performance, large port capacity, low latency, virtualization support, security, Quality of Service (QoS) etc.

Switch vs. Router

Routers select paths for data packets to cross networks and reach their destinations. Routers do this by connecting with different networks and forwarding data from network to network — including LANs, wide area networks (WANs), or autonomous systems, which are the large networks that make up the Internet.

In practice, what this means is that routers are necessary for an Internet connection, while switches are only used for interconnecting devices. Homes and small offices need routers for Internet access, but most do not need a network switch, unless they require a large number of ports. However, large offices, networks, and data centers with dozens or hundreds of computers usually do require switches.

Additional Considerations While Looking for A Switch

Now that you have a basic breakdown of the different types of switches out there, here are a few other useful things to consider:

Number of Ports

Switches can have anywhere from 5-port to 52-port configurations. When considering the number of ports you will need, you should think about the number of users your network supports. The larger your organization is, the more ports you will need.

Speed

Fixed configuration switches come in Fast Ethernet (10/100 Mbps), Gigabit Ethernet (10/100/1000 Mbps), Ten Gigabit (10/100/1000/10000 Mbps) and 40/100 Gbps speeds.

If all of this seems confusing, the biggest thing to consider when determining speed is the network needs of the users. Will they be transferring large volumes of data? Then Gigabit Ethernet or faster is likely the way to go.

PoE vs. non-PoE

Power over Ethernet (PoE) allows you to power a device like an IP phone or wireless access point over the same cable as your data traffic. If you have a larger network, PoE can provide you with great flexibility by allowing you to place endpoints anywhere in the office. This is especially handy in spaces where it is difficult to run a power outlet.

Stackable vs. Standalone

Is your network growing rapidly? Then you may want to go with a stackable switch. Standalone switches need to be configured individually and troubleshooting also needs to be handled on an individual basis.

Stackable switches allow for multiple switches to be configured as though they were one entity. One great advantage is that they can be configured. In the event of a port or cable failure, the stack of switches will automatically reroute around the failure.