What device operates at the network layer of the OSI model and forwards packets across computer networks?

Routers are networking devices operating at layer 3 or a network layer of the OSI model. They are responsible for receiving, analysing, and forwarding data packets among the connected computer networks. When a data packet arrives, the router inspects the destination address, consults its routing tables to decide the optimal route and then transfers the packet along this route.

Features of Routers

• A router is a layer 3 or network layer device.

• It connects different networks together and sends data packets from one network to another.

• A router can be used both in LANs (Local Area Networks) and WANs (Wide Area Networks).

• It transfers data in the form of IP packets. In order to transmit data, it uses IP address mentioned in the destination field of the IP packet.

• Routers have a routing table in it that is refreshed periodically according to the changes in the network. In order to transmit data packets, it consults the table and uses a routing protocol.

• In order to prepare or refresh the routing table, routers share information among each other.

• Routers provide protection against broadcast storms.

• Routers are more expensive than other networking devices like hubs,bridges and switches.

• Routers are manufactured by some popular companies like −

  • Cisco
  • D-Link
  • HP
  • 3Com
  • Juniper
  • Nortel

Routing Table

The functioning of a router depends largely upon the routing table stored in it. The routing table stores the available routes for all destinations. The router consults the routing table to determine the optimal route through which the data packets can be sent.

A routing table typically contains the following entities −

• IP addresses and subnet mask of the nodes in the network
• IP addresses of the routers in the network
• Interface information among the network devices and channels

Routing tables are of two types −

• Static Routing Table − Here, the routes are fed manually and are not refreshed automatically. It is suitable for small networks containing 2-3 routers.

• Dynamic Routing Table − Here, the router communicates with other routers using routing protocols to determine the available routes. It is suited for larger networks having large number of routers.

Types of Routers

A variety of routers are available depending upon their usages. The main types of routers are −

• Wireless Router − They provide WiFi connection WiFi devices like laptops, smartphones etc. They can also provide standard Ethernet routing. For indoor connections, the range is 150 feet while its 300 feet for outdoor connections.

• Broadband Routers − They are used to connect to the Internet through telephone and to use voice over Internet Protocol (VoIP) technology for providing high-speed Internet access. They are configured and provided by the Internet Service Provider (ISP).

• Core Routers − They can route data packets within a given network, but cannot route the packets between the networks. They helps to link all devices within a network thus forming the backbone of network. It is used by ISP and communication interfaces.

• Edge Routers − They are low-capacity routers placed at the periphery of the networks. They connect the internal network to the external networks, and are suitable for transferring data packets across networks. They use Border Gateway Protocol (BGP) for connectivity. There are two types of edge routers, subscriber edge routers and label edge routers.

• Brouters − Brouters are specialised routers that can provide the functionalities of bridges as well. Like a bridge, brouters help to transfer data between networks. And like a router, they route the data within the devices of a network.

Updated on 22-Jul-2020 08:40:25

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