Device What is does

Stands for "modulating-demodulating":

modems are hardware devices that allow a computer or another device, such as a router or switch, to connect to the Internet. They convert or "modulate" an analog signal from a telephone or cable wire to digital data (1s and 0s) that a computer can recognize.

Simply send traffic from point A to piont B without further manipulation.


Are responsible for sending data from one network to another.

Work at Layer 3 (Network) of the OSI model, which deals with IP addresses.

Typically, routers today will perform the functionality of both a router and a switch - that is, the router will have multiple ethernet ports that devices can plug into.


They use the MAC address of a device to send data only to the port the destination device is plugged into.

Work at Layer 2 (Data Link) of the OSI model, which deals with MAC addresses.


Unlike switches, hubs broadcast data to all ports, which is inefficient, so hubs are basically a multiport repeaters.

Note: it is also useful to know the following terms:

  • Default gateway - a piece of software usually located on a router, a firewall, a server, etc, that enables traffic to flow in and out of the network. Gateways act as a junction between multiple networks.

  • DHCP (Dynamic Host Configuration Protocol) - a protocol that automatically provides and assigns IP addresses, default gateways, DNS servers and other network parameters to client devices. Most routers/switches have the ability to provide DHCP server support.

    In case you have several devices on your network that support DHCP, you need to make sure that only one of them is configured with DHCP. Having several devices with DHCP enabled will lead to a DHCP Race Condition - also known as Conflicting DHCP Servers.

Note: modern voice system will require your network to have a router in it. Despite the fact that some modems have integrated router features, they barely capable of maintaining voice systems functionality. You may want to have both modem and router in your network (modem will need to  be launched in bridged mode).