A network switch is a device that connects wired devices on a local area network (LAN), such as computers, phones, printers, cameras, wireless access points and servers, and forwards traffic between them. Each device plugs into a port, and the switch learns which device is on which port so it can send traffic only where it needs to go. Switches are the backbone of an office or building network, sitting in wiring closets and data centers. Many also supply power to the devices they connect.
At a glance
- A switch forwards traffic between devices on the same local network, based on hardware (MAC) addresses.
- Managed switches add configuration and visibility: VLANs, quality of service, security features and monitoring.
- Power over Ethernet (PoE) switches power phones, access points and cameras over the network cable.
- Layer 3 switches can also route between internal networks, overlapping with some router functions.
- Key buying factors are port count and speed, uplink speed, PoE budget, management features and support lifecycle.
What problem it solves
Devices on a network need a way to reach each other and the rest of the network. Early shared networks sent every packet to every device, which wasted capacity and caused collisions. A switch gives each port its own connection and delivers traffic only to the intended port, so many conversations can happen at once at full speed.
Switches also make a building network manageable. Managed switches let administrators separate traffic into VLANs, give priority to voice and video, control which devices can connect, and see where problems occur. With PoE, the same switch can power wireless access points, phones and cameras without separate electrical outlets.
How it works
Forwarding. When a frame arrives, the switch records the sender’s MAC address against that port. It looks up the destination address and sends the frame out the matching port. Unknown destinations and broadcasts are sent to all ports in the same VLAN.
Ports and speeds. Access ports for user devices commonly run at 1 Gbps, with multi-gigabit ports increasingly used for newer access points. Uplink ports, often fiber, connect switches back to the core at higher speeds. Comparing total device demand with uplink capacity shows whether a switch may become a bottleneck.
Power over Ethernet. PoE switches supply power on the data cable. Each switch has a total power budget and per-port limits set by the PoE standard it supports, so heavy PoE loads may need larger power supplies.
Layers. A Layer 2 switch forwards within a network. A Layer 3 switch can also route between VLANs, which is common at the core of a building network.
Stacking and redundancy. Many switches can be stacked or clustered and managed as one unit, with redundant power supplies and uplinks, so one failure affects fewer users.
Management. Switches may be managed through a command line, local web interface or a cloud dashboard. Cloud-managed switches are common in SD-Branch designs, where switches, Wi-Fi and WAN share one console.
Switches typically sit in the IDF on each floor and in the main network room. For help planning a refresh, see our wired and wireless LAN infrastructure page.
When it matters for buyers
- New offices. Port counts, PoE needs and closet layout are set during fit-out.
- Wi-Fi upgrades. Newer access points may need multi-gigabit ports and more PoE power than older switches provide.
- Security and segmentation. Separating guests, IoT and staff traffic depends on managed switches and VLANs.
- End of support. Once a vendor stops releasing updates, switches become a security and support risk.
Questions to ask vendors
- How many ports, at what speeds, do we need now and in three to five years?
- What is the total PoE budget, and does it cover all planned devices with headroom?
- What uplink speeds are available, and how much oversubscription will there be?
- Are the switches managed locally or in the cloud, and what does management licensing cost?
- What are the end-of-sale and end-of-support dates for the proposed models?
- How are firmware and security updates delivered and applied?
- What redundancy is included: stacking, dual power supplies, redundant uplinks?
How it differs from a router
A switch connects devices within a local network and forwards traffic among them. A router connects different networks, such as your office LAN to the internet or to other sites, choosing paths between them and often applying network address translation and security policy. In a typical office, devices connect to switches, and switches connect to a router or firewall at the edge. Layer 3 switches blur the line by routing between internal networks, but most sites still use a router or firewall for the WAN and internet connection.