Comparison of rip, ospf and eigrp routing protocols based. Open shortest path first ospf is a linkstate routing protocol, rather than a distance vector protocol. Open shortest path first ospf is a link state routing protocol which was first defined as version 2 in rfc 2328. Path routing algorithm an overview sciencedirect topics. Prerequisite ospf fundamentals open shortest path first ospf is a linkstate routing protocol which is used to find the best path between the source and the destination router using its own shortest path first. Ospf defines the following overlapping categories of routers. Open shortest path first ospf is the first linkstate protocol that you will learn about. A simulation of the ospf election protocol shows three results. Configure ospf open shortest path first on a border router using cli commands on my managed switch.
Overview in the rip lab, we discussed a routing protocol that is the canonical example of a routing protocol built on the distancevector algorithm. Aug 10, 2005 the open shortest path first ospf protocol, defined in rfc 2328, is an interior gateway protocol used to distribute routing information within a single autonomous system. It is used to allow routers to dynamically learn routes from other routers and to advertise routes to other routers. Open shortest path first version 2 arista networks. Overview in lab 6 we discussed rip, which is the canonical example of a routing protocol built on the distancevector algorithm. Open shortest path first ospf is a routing protocol developed for internet protocol ip. Internal gateway protocol igp, routing information protocol rip, variable length subnet masks vlsm introduction. Ospf open shortest path first is the most widely used igp interior gateway protocol large enterprise networks.
Ospf uses cost as its metric, which is computed based on the bandwidth of the link. Ospf employs a hierarchical network design using areas. By collecting connectivity information from all of the devices on the network, ospf. It implements the dijkstras algorithm, also known as shortest path first spf algorithm. Pdf open shortest path first ospf routing protocol simulation. May 19, 2018 introduction to open shortest path first ospf a tutorial open shortest path first ospf is a link state routing protocol which was first defined as version 2 in rfc 2328.
This is used to allow routers to dynamically learn. This chapter focuses on a number of objectives falling under the ccnp routing principles. It uses a link state routing algorithm and falls into the group of interior routing protocols, operating within a single autonomous system as. Figure 251 shows an example of an internetwork with several areas. It falls into the group of interior gateway protocols igps, operating within a single autonomous system as. All routers run the same algorithm in parallel and from the link state database. Apr, 2020 open shortest path first ospf is a routing protocol developed for internet protocol ip networks by the interior gateway protocol igp working group of the internet engineering task force ietf. Ospf is designated by the internet engineering task force ietf as one of several interior gateway. Ospf is a common tcpip internal gateway protocol igp used to distribute routing. Ospf is a standardized linkstate routing protocol, designed to scale efficiently to.
Using the link state information which is available in routers, it constructs the topology in which the topology determines the routing table for routing decisions 7. Introduction to open shortest path first ospf protocol. Open shortest path first ospf routing protocol dummies. Ospf is an intradomain routing protocol and it is the implementation of link state routing protocol. Short for open shortest path first, an interior gateway routing protocol developed for ip networks based on the shortest path first or linkstate algorithm routers use linkstate algorithms to send routing information to all nodes in an internetwork by calculating the shortest path to each node based on a topography of the internet constructed by each node. What this means is that you can run ospf in a network consisting of multivendor devices. Open shortest path first ospf is an open standard not proprietary and it. Understanding basic open shortest path first routing principles not only applies to the ccnp certification but to all ciscobased certifications. Comparison of rip, eigrp, ospf, igrp routing protocols in. In link state algorithms a router determines the state.
The following sections describe how ospf was invented, how ospf works, and provide more ospf information. Lecture 20 routing in data networks mit opencourseware. Dijkstras algorithm each router computes its own table may have oscillations open shortest path first ospf tells neighbors about everyone exchanges distance vectors with neighbors bellman. Open shortest path first ospf routing protocol and.
Open shortest path first ospf is an adaptive routing protocol for internet protocol ip networks. Any change in routing information is flooded to all routers in the network. Ospf is based on the shortest path first spf algorithm which is used to calculate the shortest path to each node. This report discusses about the ospf protocol, its advantages, some issues. The original open shortest path first ospf is a routing protocol for internet protocol ip networks. Open shortest path first first ospf rfc oct 1989 final rfc 2328 april 1998 ospf components 1 hello protocol detect neighbors and confirm still there 2 reliable flooding mechanism ensures all routers in an ospf area have a consistent link state database ospf is encapsulated in ip and the ip protocol field is set to 0x59.
Pdf open shortest path first ospf routing protocol. Open shortest path first ospf is a dynamic, hierarchical routing protocol designed to support routing in tcpip networks. Open shortest path first ospf interior routing protocols using a distancevector routing algorithm, such as the routing information protocol rip, have a long history and work well in a small group of routers. From its name, we can tell that it is a single path algorithm. Dijkstras algorithm compute the leastcost path from one node to all other nodes in the network.
While sending ospfv3 packets, the hmacmd5 or sha algorithm hash is inserted in the ipsec. Multicast ospf mospf uses same topology data base as ospf. Ospf is an interior gateway protocoligp which helps in identifying the. Open shortest path first ospf open shortest path first ospf is a standardized linkstate routing protocol, designed to scale efficiently to support larger networks. The main advantage of ospf with respect to other intradomain routing protocols is scalability up to some hundreds of routers. You may have realized that you cannot run eigrp in a. The first two versions are used with ipv4, while version 3 is thought for ipv6. Open shortest path first ospf, which was created to replace rip routing information protocol, is a routing protocol designed for larger or more complex networks than those normally supported by rip. Apr 26, 2017 in this set of solved multiple choice question on routing protocol in computer networks includes mcqs of routing function, static routing, dynamic routing, open shortest path first ospf protocol, routing information protocolrip and autonomous system. This algorithm is used by most link state routing protocols, including ospf and isis. Jan 05, 2016 a brief tutorial on dijkstras shortest path first algorithm. Static routing is the simplest way of routing the data packets from a source to a destination. Open shortest path first a routing protocol based on the linkstate algorithm objective the objective of this lab is to configure and analyze the performance of the open shortest path first ospf routing protocol. In case of more than one equalcost route, traffic is distributed among them.
Shortest path link state routing flood link weights throughout the network compute shortest paths as a sum of link weights forward packets on next hop in the shortest path convergence process changing from one topology to another transient periods of inconsistency across routers summary. Ospfopen shortest path first configuration in cisco. Open shortest path first version 3 arista networks. Its newest implementation, version 2, which is explained in rfc 2328, is an open standard. Dijkstras algorithm is another wellknown shortest path routing algorithm. The ospf open shortest path first protocol is one of a family of ip routing protocols, and is an interior gateway protocol igp for the internet, used to distribute ip routing information throughout a single autonomous system as in an ip network. Jan 04, 2017 open shortest path first ospf is a link state routing protocol lsrp that uses the shortest path first spf network communication algorithm dijkstras algorithm to calculate the shortest connection path between known devices. Open shortest path first ospf is an open link state routing protocol. Open shortest path first ospf is a routing protocol for internet protocol ip networks. Pdf genetic algorithm finding the shortest path in networks. The open shortest path first ospf protocol is a link state protocol that handles routing for ip traffic. Oct 22, 2017 in this tutorial, we will learn how to configure our network using ospf open shortest path first in cosco packet tracer. Open shortest path first ospf was designed as an interior gateway protocol, for use in an autonomous system such as a local area network lan. The first heuristic routing algorithm partitions the destination node set d into two subsets, dh and d l, where every node in d h has a higher label than that of the source node u 0, and every node in d l has a lower label than that of u 0.
It computes the shortest path tree for each route using a method based on dijkstras algorithm, a shortest path first algorithm. Moreover, reference 2 used a genetic algorithm to solve the routing issue in road. Ospf uses the dijkstra shortest path first algorithm to determine the shortest path. Routers connect networks using the internet protocol ip, and ospf open shortest path first is a router protocol used to find the best path for packets as they pass through a set of connected networks. Open shortest path first ospf is a link state routing protocol lsrp that uses the shortest path first spf network communication algorithm dijkstras algorithm to calculate the shortest connection path between known devices. Pdf open shortest path first ospf is a dynamic, hierarchical routing protocol designed to support routing in tcpip networks. Solved mcq on routing protocol in computer networks set1. A brief tutorial on dijkstras shortest path first algorithm. Open shortest path first ospf inetdaemons it tutorials. Ospf is perhaps the most widelyused interior gateway protocol igp in large enterprise networks. It uses a link state routing lsr algorithm and falls into the group of interior gateway protocols igps, operating within a single autonomous system as. Ospf standards are covered in rfc 1245 and rfc 1583. Open shortest path first wikipedia republished wiki 2. However, they also have some serious limitations in both scalability and performance that makes them poorlysuited to larger autonomous systems or those with specific performance issues.
Open shortest path first ospf is an open standard not proprietary and it will run on most routers independent of make. This is a very high level, simplified way of looking at the various steps of the. As a linkstate routing protocol it was based on the linkstate algorithm developed for the arpanet in 1980 and the isis routing protocol. Ospf is a classless protocol, and thus supports vlsms.
For example, a router that is connected to more than one area, and which. Open shortest path first ospf is a routing protocol developed for internet protocol ip networks by the interior gateway protocol igp working group of the internet engineering task force ietf. After the kth iteration, the leastcost paths for k destination nodes are found. In this set of solved multiple choice question on routing protocol in computer networks includes mcqs of routing function, static routing, dynamic routing, open shortest path firstospf protocol, routing information protocolrip and autonomous system. Ospf routers learn the entire network topology for their area the portion of the network they maintain routes for, usually the entire network for small networks.
The linkstate information is maintained on each router as a linkstate database lsdb which is a treeimage of the entire network topology. Ford algorithm each routers table is used by others may have routing loops routing information protocol rip. The updates for ipv6 are specified as ospf version 3 in rfc 5340 2008. Shortest path first algorithm ospf uses a shorted path first algorithm in order to build and calculate the shortest path to all known destinations. Open shortest path first ospf is an intradomain routing protocol based on the link state ls algorithm. However, due to the complexity of the network traffic, multipath algorithm is needed in order to solve the problems we are facing today such as traffic congestion. Routing is a distributed algorithm react to changes in the topology compute the paths through the network shortestpath link state routing. For instance, reference 1 proposed a genetic algorithm to find the shortest path in computer networks. Basic notes on ospf open shortest path first sysnet notes. This report discusses about the ospf protocol, its advantages, some issues faced while designing large ospf networks. The ospf routing algorithm was created to provide an alternative to rip, based on. Open shortest path first ospf is a particularly efficient igp routing protocol that is faster than rip, but also more complex. Open shortest path first ein routingprotokoll neingeist entropia ev.
Open shortest path first router alley essys, aide aux. The basic idea behind dijkstras algorithm is quite different from the bellmanford algorithm or the distance vector approach. Open shortest path first version 3 open shortest path first ospf is a linkstate routing protocol that operates within a single autonomous system. In this tutorial, we will learn how to configure our network using ospfopen shortest path first in cosco packet tracer.
This paper examines how ospf works and how it can be used to design and build todays large and complicated networks. Ospf routes have an administrative distance is 110. What is open shortest path first ospf definition from. The shortest path is calculated with the use of the dijkstra algorithm. Ospf adheres to the following link state characteristics. Ospf routing protocol simulation high speed network lab. It is defined as ospf version 2 in rfc 2328 1998 for ipv4. Apart from being a linkstate protocol, it is also an open standard protocol. Ospf routes packets based entirely on the destination ip of the. Sep 27, 2012 open shortest path first ospf is an adaptive routing protocol for internet protocol ip networks.
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