Computer Networking

Transport Layer

Router And Its Functionalities

Router is the network layer device which provides best optimal path in its functionality. It is used to connect multiple LAN’s over internet through IP addressing. So, it is an internetworking device. Some popular companies (i.e. Cisco, HP, 3Com, Juniper, D-Link, Nortel) are developing routers.

Keep in mind the HUB, Switch and Bridge are networking devices which create networks but Router is internetworking device rather than a networking device which connects the networks.

  • Every router holds multiple interfaces to connect multiple LAN’s.
  • Each interface holds its own Network ID (IP address).
  • The different Network-ID’s which are assigned to different interfaces of router are derived from their belonging LAN. IP address of One Network ID can’t exist in any other Network ID.
  • Assign IP to interface of Router is called the default gateway of Belonging LAN. So, different networks hold different gateways to connect with router interface.

Note: Gateway is entering or exist point in the network.

Router and its Functionalities

Routing Table

There are millions of networks and thousands of routers which are connected with each other over the internet.
If a node from one network wants to send message to other node of any other network, then message first goes to router, and then router use its routing table for optimal path delivery.
There may be several subnets are connected to a single router but there will be single routing table for each router.

Entries of Routing Table

A routing table holds the necessary information’s to forward a packet through optimal path. Routing Table helps the router for sending the packet to the next hop in the network. Each entry in the routing table involves the following entries

1. Network ID: It represent the destination corresponding to the route.
2. Subnet Mask: the mask that is used to match a destination IP address to the network ID.
3. Next Hop: It is an IP address of next Hope (Router), to which the packet is forwarded.
4. Interface: Interface is an outgoing point, initially through this interface; the packet can go out to reach the destination network. Remember, every router holds at least 2 interfaces.
5. Metric: It tells the minimum number of hops (routers) crossed to the network ID. it identify the route having the fewest hops. It helps to minimize the “cost of the route.”

Working of Router

Router is an intelligent inter-networking device. It is responsible for routing the data packets from source to destination. On end of router is connected to Modem and rest interface of router is used to connect (either wired or wireless) networking devices such as PC, Laptop, Mobile phone, tablet, etc.
In various forms,

  • Router can directly connect to single or more devices with cable using Router ports.
  • Router is connected to switch then various devices are connected with switch.

Routers are of two types in connection, wired and wireless. Wired Router connects devices through some cables i.e. (Ethernet) but wireless use Wi-Fi instead of cable. The Wired Routers are generally having faster speed. Router transmits the data packets by using IP address. It transmits data from one network to another or within a network.

Working of Routing in Networking

Types of Router

There are different types of the router, some types are given under

  • Wireless Router
  • Wired Router/Broadband Router
  • Edge Router
  • Core Router
  • Virtual Router

Important: We can access the internet without using a router.

Functionalities of Router

There are various types of the router functionalities, some of them are given under

  • Routing
  • Store and Forwarding
  • Flooding
  • Filtering
  • Collision

Comparison of Router and Switch

The comparison of Router and switch is given below

Switch Router

Switch is capable to communicate all devices within same network by using same network ID

Router is capable to communicate all devices existing in network by using different network ID
Switch looks similar to Router but It holds lot of ports Router also looks similar to Swich but generaly holds 2, 4, or 8 ports.
It use in local area network .  It is mostly used in WAN.  It may rarly used in LAN but costly than switch.
Communication devices are directly connected with Switch Generally, Routers are connected with switches, not directly connected with devices

Router Assign Private IP address to each device connected to it. 

In next lecture we will see the difference in Public and Private IP address.

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