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What is Router and its function ?

What is Router and its function ?

What is Router and its function ?

Router is a device, used in computer networking. It is layer three (Network Layer) device. It forwards the packet on the basis of Routed Protocols such as IP, IPv6, IPX etc.

This device is generally used to communicate between two or more than two different segment, different network or LAN. It means If you have two identical LAN, established in two different location such as New York and Arizona. And you want to make connection between them, Router can solve your problem.

Geographical identity does not matter, Router can be used within a building too.


Router has generally three main functions.

  • Packet Forwarding
  • Packet switching and
  • Packet filtering


Router maintains a routing table for all possible networks those can be reached. In the routing table, a router maintains, subnet, Gateway, forwarding interface, timing etc of the destination network. If multiple paths exist to reach the destination network, only best path is maintained in the routing table.

Once any packet is received, it checks the destination IP network in the routing table. If destination network is available in routing table, It forwards the packet otherwise it drops.


To move packets from one interface to another to get a packet to its destination.


Packet filtering is such like firewall. By which you can define which network can be entered and which network can be dropped. In easy word, It filters the packet on the basis of IP address, subnet, port no and protocols.


Cisco Routers can be found two types


Fixed routers are that type of router which has fixed slot and interface such as : 2500 series routers.


Modular routers are that type of router which has not fixed slot and interface and you can install interface and slot as per your requirement. Such as : 2600, 2800 series etc.


  • It is layer 3 devices.
  • Used to communicate among different networks
  • Forwards packet on the basis of routed protocol. Such as IP, IPv6, IPX etc.
  • It has main three functions: Packet Forwarding, Packet switching and Packet filtering.
  • Every interface is single broadcast domain.
  • Every interface with Ethernet is single collision domain.
  • It creates routing table and maintain possible network to be reached.
  • It chooses best path, if multiple path is exist.
  • Packet will be dropped if destination network is not found in routing table.
  • It has two types: 1) Fixed and 2) Modular

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