Network router explained

A router is a network device that routes packets from one network to another. It is usually connected to two or more different networks. When a packet comes to a router port, the router reads the address information in the packet to determine out which port the packet will be sent. For example, a router provides you with the internet access by connecting your LAN with the Internet.

A router is most commonly an OSI Layer 3 device, since its forwarding decision is based on the information of the OSI Layer 3 – the destination IP address. Routers divide broadcast domains, provide full duplex communication, and have traffic filtering capabilities.


The picture below shows a typical home router:

Typical home router

If two hosts from different networks want to communicate, they will need a router in order to exchange data. Consider the following example:

Network router explained

We have a network of three hosts and a router. Note that each computer is on a different network. Host A wants to communicate with Host B and sends the packet with the Host B’s IP address ( to the router. The router receives the packet, compares the packet’s destination IP address to the entries in its routing table and finds a match. It then sends the packet out the interface associated with the network Only Host B will receive and process the packet. In fact, Host C will not even be aware that the communication took place.

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