Introduction to IP Routing

Switching:

• We have seen about Switches, and how switches works.
• The only concern of the Switch is to know when a Ethernet frame enters the Switch and on which interface it has to exit.
• Switches works on Data-link Layer (Layer 2).
• Switches stores the MAC-Address table to forward frames.

Routing:

• Similar to the Switch, Router also works by storing information, but it stores about IP Packets.
• IP Packets lives in Network Layer (Layer 3 ).
• Routers looks at Destination IP Address in an IP packet and send it out to the correct Interface.

Why use Router Instead of Switch ?

• We have 2 Switches and each Switch is connected to 50 computers.
• Each Switch should share their learned MAC-Address, so what happens..?
• Each switch having a large mac-address table. 
• For this Network, it seems to be OK.
• Consider, if its connected to a very large network like internet, there are billions of devices its impossible to store all the information in the device, but this can be handled by using Routers.

How Router stores Information

• If you see the above picture, Routing table stores the information about only the IP Address of the segment and not the Mac-Address.
• In order to get information about the Networks behind other Routers, Routing Protocols are Mandatory for Every Router.
• So, R1 has the information of 192.168.3.0/24 is behind R2. & R2 has an information 
• of 192.168.2.0/24 is behind R1.

Routing Protocols

• There are 2 Routing Protocols
• Static 
• Dynamic
• Static Protocols
• We need to manually Configure the Destination IP Segment and Next-hop IP Address or Exit Interface of the Router.
• Protocol used : Static Route
• Dynamic Protocols
• Networks Beyond other Devices will be automatically fetched from the Routing Protocols
• Protocol used : RIP, EIGRP, OSPF.

That's it 

You can also Look into my Video Tutorial

Introduction to IP Routing