How does routing protocol work

Dynamic routing protocols are another important type of routing protocol. It helps routers to add information to their routing tables from connected routers automatically. Distance Vector Protocols advertise their routing table to every directly connected neighbor at specific time intervals using lots of bandwidths and slow converge.

In the Distance Vector routing protocol, when a route becomes unavailable, all routing tables need to be updated with new information. It also runs on the Application layer of the OSI model. Two versions of RIP are. The original version or RIPv1 helps you determine network paths based on the IP destination and the hop count journey. RIPv1 also interacts with the network by broadcasting its IP table to all routers connected with the network.

It is introduced to overcome RIP limitations. The metrics used are load, bandwidth, delay, MTU, and reliability. It is widely used by routers to exchange routing data within an autonomous system. This type of routing protocol is the best for larger network size as it broadcasts after every 90 seconds, and it has a maximum hop count of It helps you to sustain larger networks compared to RIP.

IGRP is also widely used as it is resistant to routing loop because it updates itself automatically when route changes occur within the specific network.

It is also given an option to load balance traffic across equal or unequal metric cost paths. Link State Protocols take a unique approach to search the best routing path. It can also be called an act of approach to a state where all routing tables have detailed information are in a steady-state. The convergence time, which is updated by the router, should reflect the exact details about the values is known as accuracy.

The routing update mechanism is a process of information transfer between the neighboring routers. This can be explained as follows while routing at a particular time duration router to advertise its data information through broadcast or multicast.

Various routing protocols have various time intervals. These routing updates contain information on routing protocols such as AS, AD, matrix values, and interface details. Autonomous system: AS can be defined as a collection of routers with similar routing table information, simply defined as the boundary line for routing protocol. It can be one-to-one or one-to-many and can also be defined by a numeric value. As numbers define it, an internet assigned numbers authority provided a range from Interior gateway protocols: These are used in data transfer to share routing information between routers in the same autonomous system.

Exterior gateway protocols: These are used in data transfer to share routing information between routers in the different autonomous systems. An example of exterior gateway protocols is the Border gateway protocol.

Administrative distance: AD can be defined as the reliability of routing updates received from the neighboring router. For example, if two updates are received for the same path from two routing protocols, the router will check the best AD value to choose the optimistic path.

The AD with the lowest value will be given more preference. Metric: If two routing updates have the same Ad value, then the metric will come in to picture to calculate the best path. Similar to AD, different routing protocols use different metric values. The routing protocol with the lowest value will be selected. The routing protocols can be mainly classified into three types. Each of these has its own importance in data transfer. Let us now discuss in detail each of these protocols in detail.

This mainly uses distance as the metric value and direction as a vector to select the optimal path to the destination network. Basically, the router receives the routing information from neighboring routers, which receives this information from their neighboring router until the destination network. Each neighboring router in the path of a destination network is called a hop. These protocols measure the distance based on how many hops data has to pass to get to its destination.

The number of hops is essentially the number of routers it takes to reach the destination. Generally, distance vector protocols send a routing table full of information to neighboring devices. This approach makes them low investment for administrators as they can be deployed without much need to be managed. The only issue is that they require more bandwidth to send on the routing tables and can run into routing loops as well.

Link state protocols take a different approach to finding the best routing path in that they share information with other routers in proximity. The route is calculated based on the speed of the path to the destination and the cost of resources. Link state routing protocols use an algorithm to work this out. Routers using the link state protocol creates three types of tables; neighbor table , topology table , and routing table. The neighbor table stores details of neighboring routers using the link state routing protocol, the topology table stores the whole network topology, and the routing table stores the most efficient routes.

IGPs are routing protocols that exchange routing information with other routers within a single autonomous system AS. An AS is defined as one network or a collection of networks under the control of one enterprise. On the other hand, EGPs are routing protocols that are used to transfer routing information between routers in different autonomous systems.

The original version or RIPv1 determines network paths based on the IP destination and the hop count of the journey. RIPv1 interacts with the network by broadcasting its IP table to all routers connected to the network.

RIPv2 is a little more sophisticated than this and sends its routing table on to a multicast address. RIPv2 also uses authentication to keep data more secure and chooses a subnet mask and gateway for future traffic. The main limitation of RIP is that it has a maximum hop count of 15 which makes it unsuitable for larger networks.

See also: LAN Monitoring tools. IGRP was designed to build on the foundations laid down on RIP to function more effectively within larger connected networks and removed the 15 hop cap that was placed on RIP.

IGRP uses metrics such as bandwidth, delay, reliability, and load to compare the viability of routes within the network. IGRP is ideal for larger networks because it broadcasts updates every 90 seconds and has a maximum hop count of This allows it to sustain larger networks than a protocol like RIP.

IGRP is also widely used because it is resistant to routing loops because it updates itself automatically when route changes occur within the network. The SPF routing algorithm is used to calculate the shortest path spanning-tree to ensure efficient data transmission of packets. OSPF routers maintain databases detailing information about the surrounding topology of the network. LSAs are packets that detail information about how many resources a given path would take.

OSPF also uses the Dijkstra algorithm to recalculate network paths when the topology changes. This protocol is also relatively secure as it can authenticate protocol changes to keep data secure. Topology changes are tracked and OSPF can recalculate compromised packet routes if a previously-used route has been blocked.

Exterior Gateway Protocol or EGP is a protocol that is used to exchange data between gateway hosts that neighbor each other within autonomous systems.

In other words, EGP provides a forum for routers to share information across different domains. The most high profile example of an EGP is the internet itself. The routing table of the EGP protocol includes known routers, route costs, and network addresses of neighboring devices.

The EGP protocol works by keeping a database of nearby networks and the routing paths it could take to reach them. This route information is sent on to connected routers. Once it arrives, the devices can update their routing tables and undertake more informed path selection throughout the network. Neighbors are queried for a route and when a change occurs the router notifies its neighbors about the change.

This has the end result of making neighboring routers aware of what is going on in nearby devices.