Enterprise switches and routers are the boxes that wire an office network together and connect it to the outside world. A switch joins the devices inside a building: access points, desk computers, desk phones and printers. A router joins one network to another, such as the office to the internet or to the company's other offices.
A switch is a box with many sockets for network cables, often 24 or 48. Each device is plugged into one socket. When data arrives, the switch reads the address of the device that the data is meant for. It then sends the data out of the one socket that leads to that device. The switch keeps a table of which device is on which socket, so it does not have to send the data to everyone.
Consider a logistics company's office in Gurugram with three floors and 250 staff. On each floor, a cupboard holds two 48-port switches. These are called access switches, because the devices connect to them. Every desk, every ceiling Wi-Fi access point, every desk phone and every printer has a cable to one of them. The access switches on all three floors connect to two larger switches in the ground-floor server room, called core switches. There are two core switches, so that the office keeps working if one of them fails. Finally, a router connects the core switches to two internet lines from two different providers.
When an employee on the third floor prints a delivery report on the first-floor printer, the data goes from her laptop to the third-floor switch, down to a core switch, across to the first-floor switch, and into the printer. It never leaves the building, and the router plays no part.
Switches also keep groups apart, using VLANs, or virtual local area networks. A VLAN is a separate network created in software on the same cables. The company puts the accounts team, the guest Wi-Fi and the security cameras on different VLANs. So a guest cannot reach the accounts computers, even though both use the same switches.
Many switch sockets also supply electricity over the network cable. This is called power over Ethernet (PoE). It powers the access points, desk phones and cameras, so they need no separate power sockets.
When a device first asks for an address, the switch forwards the request to the DDI system. Before letting a new device on, the switch can ask network access control to check it.
Office switches are different from data centre switches, which connect thousands of servers at much higher speeds. And in branch offices, the single router is often replaced by SD-WAN, which uses several cheaper internet links and is managed centrally.