Types of Routing

Routing is the process of determining paths through a network for sending data packets. It ensures that data moves effectively from source to destination, making the best use of network resources and ensuring consistent communication.

Routing is performed by layer 3 (or network layer) devices to deliver the packet by choosing an optimal path from one network to another. It is an autonomous process handled by the network devices to direct a data packet to its intended destination. The node here refers to a network device called Router.

Types of Routing

Routing is typically of 3 types, each serving its purpose and offering different functionalities.

1. Static Routing

Static routing is also called as “non-adaptive routing”. In this, routing configuration is done manually by the network administrator. Let’s say for example, we have 5 different routes to transmit data from one node to another, so the network administrator will have to manually enter the routing information by assessing all the routes.

Advantages of Static Routing

• No routing overhead for the router CPU which means a cheaper router can be used to do routing.
• It adds security because only an only administrator can allow routing to particular networks only.
• No bandwidth usage between routers.

Disadvantage of Static Routing

• For a large network, it is a hectic task for administrators to manually add each route for the network in the routing table on each router.
• The administrator should have good knowledge of the topology. If a new administrator comes, then he has to manually add each route so he should have very good knowledge of the routes of the topology.

Configuration of Static Routing

R1 having IP address 172.16.10.6/30 on s0/0/1, 192.168.20.1/24 on fa0/0. 
R2 having IP address 172.16.10.2/30 on s0/0/0, 192.168.10.1/24 on fa0/0. 
R3 having IP address 172.16.10.5/30 on s0/1, 172.16.10.1/30 on s0/0, 10.10.10.1/24 on fa0/0. 

Now because only static routes for router R3: 

R3(config)#ip route 192.168.10.0 255.255.255.0 172.16.10.2
R3(config)#ip route 192.168.20.0 255.255.255.0 172.16.10.6

Here, provided the route for the 192.168.10.0 network where 192.168.10.0 is its network I'd and 172.16.10.2 and 172.16.10.6 are the next-hop address. 
Now, configuring for R2: 

R2(config)#ip route 192.168.10.0 255.255.255.0 172.16.10.1
R2(config)#ip route 10.10.10.0 255.255.255.0 172.16.10.1
R2(config)#ip route 172.16.10.0 255.255.255.0 172.16.10.1

Similarly for R1: 

R1(config)#ip route 192.168.20.0 255.255.255.0 172.16.10.5
R1(config)#ip route 10.10.10.0 255.255.255.0 172.16.10.5
R1(config)#ip route 172.16.10.0 255.255.255.0 172.16.10.5

2. Default Routing

This is the method where the router is configured to send all packets toward a single router (next hop). It doesn't matter to which network the packet belongs, it is forwarded out to the router which is configured for default routing. It is generally used with stub routers. A stub router is a router that has only one route to reach all other networks. 

Advantages of Default Routing

• Default routing provides a “last resort” route for packets that don’t match any specific route in the routing table. It ensures that packets are not dropped and can reach their intended destination.
• It simplifies network configuration by reducing the need for complex routing tables.
• Default routing improves network reliability and reduces packet loss.

Disadvantages of Default Routing

• Relying solely on default routes can lead to inefficient routing, as it doesn’t consider specific paths.
• Using default routes may introduce additional network latency.

Configuration of Default Routing

Using the same topology which we have used for static routing before.

In this topology, R1 and R2 are stub routers so we can configure default routing for both these routers.  Configuring default routing for R1: 

R1(config)#ip route 0.0.0.0 0.0.0.0 172.16.10.5

Now configuring default routing for R2: 

R2(config)#ip route 0.0.0.0 0.0.0.0 172.16.10.1

3. Dynamic Routing

Dynamic routing makes automatic adjustments of the routes according to the current state of the route in the routing table. Dynamic routing uses protocols to discover network destinations and the routes to reach them. RIP and OSPF are the best examples of dynamic routing protocols. Automatic adjustments will be made to reach the network destination if one route goes down. A dynamic protocol has the following features: 

• The routers should have the same dynamic protocol running in order to exchange routes.
• When a router finds a change in the topology then the router advertises it to all other routers.

Advantages of Dynamic Routing

• Easy to configure.
• More effective at selecting the best route to a destination remote network and also for discovering remote networks.

Disadvantage of Dynamic Routing

• Consumes more bandwidth for communicating with other neighbors.
• Less secure than static routing.

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Article Tags :

• Misc
• Computer Networks
• GATE CS

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