Routers are used by many people today. But do you know a router? You know what are your main functions? Then read this article and learn a little more of that great known – but poorly understood – by people in general.

Router is a network device that forwards data packets to many different networks. It operates at Layer 3 of the OSI Model with the TCP/IP protocol.


CISCO  Router Model 976

The router can be connected to two or more line’s data with different networks. For this, the router reads the address that is contained in the packet header and forwards it to the correct network.

Before sending the packet to the destination network, it checks on its security policies, previously set by your administrator, if the package may or may not be sent. If you can not be sent, the packet is discarded.


The router uses routing tables to decide which network routing each received packet. It makes the maintenance of these tables running processes and updates routes, assigning routing metrics.



Example of Wi-Fi router.

The administrator can configure static routes for the propagation of the packages or configure the router to automatically update their routing tables dynamically. Thus, we can say that there are two types of routers: static and dynamic.

When multiple routers are used in interconnected networks, they exchange information about destination address using a dynamic routing protocol. Each router builds a table listing the preferred routes between any of the systems on interconnected networks.

A router has interfaces to different physical types of network connections, such as copper cables, optical fiber or wireless transmission. It also contains firmware for different network communication protocol standards. Each firmware uses this interface to enable the transmission of data packets between different transmission protocols systems.

Routers can also be used to connect two or more logical groups of devices of computer, known as subnets, each with a different subnet address. The subnet addresses registered in the router does not necessarily trace routes directly to the physical interface connections.

Operation stages

A router has two operation stages named as planes:

  • Control plan:
    The router maintains a routing table that lists which route should be used to transmit a data packet, and through which physical interface. For this, it uses pre-configured policies internally known as static routes or learning to use routes with dynamic routing protocol. The static and dynamic routes are stored in the Routing Information Base (RIB).
  • Routing Plan:
    The router forwards data packets between input and output interfaces. Forwards them to the correct type of network using the information that the packet header contains, using the data recorded in the routing plan of the routing table.

CISCO Router 1900 Series

Briefly, we can say that the router is a key element for the correct operation of the network happen.

To the next!

Has errors in translation? Then let us know by sending a comment.

References: wikipedia in English and Portuguese.

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