What are Routers in Computer Network?

Routers are networking devices operating at layer 3 or a network layer of the OSI model. They are responsible for receiving, analyzing, 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 that operates using IP addresses.

• 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 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 using routing protocols.

• Routers provide protection against broadcast storms by creating separate broadcast domains.

• Routers are more expensive than other networking devices like hubs, bridges, and switches due to their advanced processing capabilities.

How Routers Work

When a router receives a data packet, it follows these steps:

• Packet Reception − Router receives the packet on one of its interfaces.

• Address Examination − Router examines the destination IP address in the packet header.

• Routing Table Lookup − Router consults its routing table to find the best path to the destination network.

• Packet Forwarding − Router forwards the packet through the appropriate interface toward the destination.

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:

• Network destination addresses and subnet masks
• Gateway or next-hop router IP addresses
• Interface information and metric values for route selection

Types of Routers

• Wireless Router − Provides WiFi connectivity to wireless devices like laptops and smartphones. Also supports standard Ethernet connections with a range of 150 feet indoors and 300 feet outdoors.

• Broadband Routers − Used to connect to the Internet through telephone lines and support Voice over Internet Protocol (VoIP) technology. They are typically configured by Internet Service Providers (ISPs).

• Core Routers − High-performance routers that route data packets within a network's backbone. They form the central infrastructure of large networks and are used by ISPs and communication providers.

• Edge Routers − Located at the network periphery, they connect internal networks to external networks. They use Border Gateway Protocol (BGP) and include subscriber edge routers and label edge routers.

• Brouters − Hybrid devices combining router and bridge functionality. They can route packets between networks and bridge traffic within the same network segment.

Conclusion

Routers are essential Layer 3 devices that enable communication between different networks by forwarding packets based on IP addresses. They use routing tables and protocols to determine optimal paths, making them fundamental components of modern network infrastructure.