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Significance and operation of router

Short answer

Routers connect networks, forward packets via IP addresses, select optimal paths, separate broadcast domains, provide security/NAT, and interconnect diverse link technologies. Operation: receive frame, verify CRC, strip L2 header, lookup destination IP via longest prefix match, decrement TTL, recalc checksum, resolve next-hop MAC via ARP, encapsulate in new frame, transmit.

Discuss the significance of router in computer networking along with its operation.

A router is a layer-3 device that connects different networks and forwards packets between them using the destination IP address.

Significance

  • Connects LANs to each other and to the Internet / WAN.
  • Selects the best path using routing tables and protocols.
  • Separates broadcast domains, so broadcasts do not flood the entire network.
  • Provides security and control: ACLs, NAT, firewall features.
  • Joins different link technologies (Ethernet to serial/DSL) and fragments packets if needed.
  • Provides DHCP, QoS and load balancing in practice.

Operation (forwarding a packet)

  1. The router receives a frame on an interface, checks the frame (CRC) and removes the layer-2 header.
  2. It reads the destination IP address from the IP header and verifies the header checksum.
  3. It looks up the routing table using the longest prefix match; if nothing matches, it uses the default route or drops the packet.
  4. It decrements TTL (if 0, drops and sends ICMP time exceeded) and recalculates the checksum.
  5. It finds the next-hop MAC address (ARP table) and builds a new frame for the outgoing link.
  6. It queues the packet and transmits it on the outgoing interface.
LAN A --[ R1 ]-- WAN --[ R2 ]-- LAN B
        table:           table:
      B -> via R2      B -> direct

Meanwhile, a routing protocol (RIP/OSPF) updates the routing table with neighbouring routers.

✓ Answer checked by Claude Opus 5.5 (high effort)

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