NETWORK ROUTING AND SWITCHING

What Is Network Routing

Routing is the process of selecting a path for traffic in a network or between or across multiple networks. … Packet forwarding is the transit of network packets from one network interface to another. Intermediate nodes are typically network hardware devices such as routers, gateways, firewalls, or switches.

Routing is a process which is performed by layer 3 (or network layer) devices in order to deliver the packet by choosing an optimal path from one network to another. There are 3 types of routing: 1. Static routing – Static routing is a process in which we have to manually add routes in routing table

Types of Routing

  • Difficulty Level : Easy
  •  Last Updated : 23 Dec, 2020

Routing is a process which is performed by layer 3 (or network layer) devices in order to deliver the packet by choosing an optimal path from one network to another. 

There are 3 types of routing: 
1. Static routing – 
Static routing is a process in which we have to manually add routes in routing table. 
Advantages – 
 

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

Disadvantage – 
 

  • For a large network, it is a hectic task for administrator 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 – 

R1 having IP address 172.16.10.6/30 on s0/0/1, 192.168.10.1/24 on fa0/0. 
R2 having IP address 172.16.10.2/30 on s0/0/0, 192.168.20.1/24 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 configuring 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 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 192.168.20.0 255.255.255.0 172.16.10.1
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 192.168.10.0 255.255.255.0 172.16.10.5
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 towards a single router (next hop). It doesn’t matter to which network the packet belongs, it is forwarded out to router which is configured for default routing. It is generally used with stub routers. A stub router is a router which has only one route to reach all other networks. 
Configuration – 
Using the same topology which we have used for the 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 adjustment 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 it. RIP and OSPF are the best examples of dynamic routing protocol. Automatic adjustment will be made to reach the network destination if one route goes down. 

A dynamic protocol have following features: 
 

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

Advantages – 
 

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

Disadvantage – 
 

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

What Is Network Switching?

Network switching is the process of channeling data received from any number of input ports to another designated port that will transmit the data to its desired destination. The device through with the input data passes is called a switch. Data entering a port is referred to as ingress, while data leaving the port is referred to as egress. The switch represents the medium through which the data is routed to its final destination. There are different types of network switching. To better understand this let us examine the following illustration.

Let us image a room full of people. In two opposite corners of the room are two connected telephones. We identify four people in the room. Two use the telephone lines to speak to each other while the other two stand across the crowded room from each other projecting their voices amid the other voices in the crowded room. These sets of people are using two different types of switching.

Circuit Switching

Circuit switching is defined as the establishment of a dedicated communication path between the two parties, or nodes, within a physical network. This path (circuit) is established and maintained for the duration of the session. No matter the length of the communication session, the circuit will remain and the data paths maintained. The circuit is only terminated when the session ends. The session consists of three phases: circuit establishment, data transfer, and circuit termination/disconnect.

This type of network switching is well suited for voice communications and applications. In our illustration, the two people communicating on the telephone lines from across the room are using a dedicated communication path. Their voices (data) follow a dedicated path. Figure 1 illustrates circuit switching.

Circuit Switch

Packet Switching

Packet switching is defined as the process of breaking down messages into small components, called packets. Switching information (source and destination) is then included in the header information of the packet. Each packet then independently navigates its way using the information, through the network to its destination. Because the messages transmitted are smaller packets, there is less demand for resources on intermediate network devices.

Packet Switching

With this system of switching, line efficiency during transmission is increased and multiple applications can be easily multiplexed over a single channel with different streams of packets differentiated and prioritized. In this type of transmission, the packets from different applications share resources. When we think of our example in the beginning, the two people projecting their voices in the crowded room are sharing the air space to transmit their data with the rest of the crowd while the other two people over the telephone are on an exclusive line.

Benefits or advantages of Switches

Following are the benefits or advantages of Switches:
➨They increase the available bandwidth of the network.
➨They help in reducing workload on individual host PCs.
➨They increase the performance of the network.
➨Networks which use switches will have less frame collisions. This is due to the fact that switches create collision domains for each connection.
➨Switches can be connected directly to workstations.

Drawbacks or disadvantages of Switches

Following are the disadvantages of Switches:
➨They are more expensive compare to network bridges.
➨Network connectivity issues are difficult to be traced through the network switch.
➨Broadcast traffic may be troublesome.
➨If switches are in promiscuous mode, they are vulnerable to security attacks e.g. spoofing IP address or capturing of ethernet frames.
➨Proper design and configuration is needed in order to handle multicast packets.
➨While limiting broadcasts, they are not as good as routers.

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