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What is the difference between a router and a modem?

Answer: Routers and modems are two of the most common computer peripherals, yet many people do not know the function of each one. While the two devices may look similar, they each serve a different purpose. Fortunately, the functions of the two devices are pretty easy to understand.

A router is a small box that allows multiple computers to join the same network (see below).

Netgear Router

While early routers only had Ethernet ports for wired connections, most modern routers provide wireless connectivity as well. "Wireless routers" often have one or two moveable antennas, though some models keep the antennas inside the enclosure. Wireless routers allow multiple computers and other devices, such as smartphones and tablets, to join the same network.

Connecting to a router provides access to a local network (LAN), but it does not necessarily provide access to the Internet. In order for devices on the network to connect to the Internet, the router must be connected to a modem. Therefore, most routers have a specific Ethernet port that is designed to connect to the Ethernet port of a cable or DSL modem.

A modem is a device that provides access to the Internet (see below).

Cisco Cable Modem

The modem connects to your ISP, which typically provides either cable or DSL Internet service. Cable modems have a coaxial (or "coax") connection, which is the same type of connector found on a TV or cable box. This connects to a cable port on the wall. DSL modems have a telephone connector, also called an RJ-11 jack, which connects to a telephone socket on the wall.

By connecting your modem to your router (instead of directly to a computer), all devices connected to the router are connected to the modem, and therefore, the Internet. The router provides a local IP address to each connected device, but they will all have the same external IP address, which is assigned by your ISP.

To summarize, the device connection order is outlined below:

  1. PC or wireless device
  2. Router
  3. Modem
  4. ISP
  5. Internet

Important: While the router and modem are often separate entities, it has been more common for the modem and router to be combined into a single device. This type of hybrid device (sometimes called a gateway) is offered by some ISPs to simplify the setup process.

Published: January 3, 2013   —   Updated: July 16, 2018 — by Per Christensson

Answer from the PC Help Center