ROUTING PROTOCOLS

What is a router in networking?

A router is a piece of network hardware responsible for forwarding packets to their destinations. Routers connect to two or more IP networks or subnetworks and pass data packets between them as needed. Routers are used in homes and offices for setting up local network connections. More powerful routers operate all over the Internet, helping data packets reach their destinations.

What is network routing?

Network routing is the process of selecting a path across one or more networks. The principles of routing can apply to any type of network, from telephone networks to public transportation. In packet-switching networks, such as the Internet, routing selects the paths for Internet protocol(IP) packets to travel from their origin to their destination. These Internet routing decisions are made by specialized pieces of network hardware called routers

Consider the image below. For a data packet to get from Computer A to Computer B, should it pass through networks 1, 3, and 5 or networks 2 and 4? The packet will take a shorter path through networks 2 and 4, but networks 1, 3, and 5 might be faster at forwarding packets than 2 and 4. These are the kinds of choices network routers constantly make.

Routing can be classified into three categories:

Static Routing
Default Routing
Dynamic Routing

Static Routing

Static Routing is also known as Nonadaptive Routing.
It is a technique in which the administrator manually adds the routes in a routing table.
A Router can send the packets for the destination along the route defined by the administrator.
In this technique, routing decisions are not made based on the condition or topology of the networks

Advantages Of Static Routing

Following are the advantages of Static Routing:

No Overhead: It has ho overhead on the CPU usage of the router. Therefore, the cheaper router can be used to obtain static routing.
Bandwidth: It has not bandwidth usage between the routers.
Security: It provides security as the system administrator is allowed only to have control over the routing to a particular network.

Disadvantages of Static Routing:

Following are the disadvantages of Static Routing:

For a large network, it becomes a very difficult task to add each route manually to the routing table.
The system administrator should have a good knowledge of a topology as he has to add each route manually.

Default Routing

Default Routing is a technique in which a router is configured to send all the packets to the same hop device, and it doesn’t matter whether it belongs to a particular network or not. A Packet is transmitted to the device for which it is configured in default routing.
Default Routing is used when networks deal with the single exit point.
It is also useful when the bulk of transmission networks have to transmit the data to the same hp device.
When a specific route is mentioned in the routing table, the router will choose the specific route rather than the default route. The default route is chosen only when a specific route is not mentioned in the routing table.

Dynamic Routing

It is also known as Adaptive Routing.
It is a technique in which a router adds a new route in the routing table for each packet in response to the changes in the condition or topology of the network.
Dynamic protocols are used to discover the new routes to reach the destination.
In Dynamic Routing, RIP and OSPF are the protocols used to discover the new routes.
If any route goes down, then the automatic adjustment will be made to reach the destination.

The Dynamic protocol should have the following features:

All the routers must have the same dynamic routing protocol in order to exchange the routes.
If the router discovers any change in the condition or topology, then router broadcast this information to all other routers.

Advantages of Dynamic Routing:

It is easier to configure.
It is more effective in selecting the best route in response to the changes in the condition or topology.

Disadvantages of Dynamic Routing:

It is more expensive in terms of CPU and bandwidth usage.
It is less secure as compared to default and static routing