Ospf guide cisco pdf the open shortest path first ospf protocol, defined in rfc 2328, is an interior gateway protocol used to distribute routing information within. Further your knowledge of the ospf for your ccna certification by answering the following questions. 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. Basic ospf configuration for internal router abr and asbrs 44. In the world of networking, the open shortest path first ospf routing protocol for ip networks uses a link state routing algorithm and is classed as an interior gateway protocol. It is an interior gateway protocol igp specifically designed to distribute unicast topology information among routers belonging to a single autonomous system. Like all linkstate protocols, ospf is very efficient in its use of network. This memo documents version 2 of the ospf protocol. The working group was formed in 1988 to design an igp based on the. Routing protocol packets share a common protocol header routing protocol packets are sent with type of service tos of 0 five types of ospf routing protocol packets hello packet type 1 database description packet type 2 linkstate request packet type 3 linkstate update packet type 4 linkstate acknowledgement.
In this lesson ill explain the basics of ospf to you and you will learn how and why it works. Ospf version 2 is documented in rfc 1583 a lengthy document that i find very difficult to read. Ospf works on a large network because there is no limitation of the number of cops in the network. Sanctioned by the ietf, it is intended to become internets preferred interior routing protocol. Ospf adheres to the following link state characteristics. 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. The ospf mib defines an ip routing protocol that provides management information related to ospf and is supported by.
The ospf network command uses a combination of networkaddress and wildcardmask. For linkstate routing protocol, it is required that the linkstate databases for all routers remain synchronized. Open shortest path first ospf was designed as an interior gateway protocol igp, for use in an autonomous system such as a local area network lan. Once you are in the router ospf configuration submode, configure the lan network 172. It uses a link state routing algorithm and falls into the group of interior routing protocols, operating within a single autonomous system as. First, when a router running ospf comes up it will send hello packets to discover its neighbors and elect a designated router. When a link state router begins operating on a network link, information associated with that logical network is added to its local link state database lsdb. Ospf ospf open shortest path first is a linkstate routing protocol that was developed in 1991. It is designed to be run internal to a single autonomous system. Ip routing protocolss dense style rewards readers willing to study the words carefully and draw meaning from the utilitarian conceptual drawings. All routers in the same ospf area must have the same process id if they are to exchange routing information. To remove an areas authentication specification or a specified area from the.
Difference between rip and ospf difference between. The first two versions are used with ipv4, while version 3 is thought for ipv6. A c question 2 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. Instead of looking at hopcount like rip, ospf looks at. On the vulnerabilities and protection of ospf routing protocol. Ospf will form neighbor relationships with adjacent routers in the same area. 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. Open shortest path first open shortest path first ospf is an openstandard link state routing protocol. Ospf protocol analysis status of this memo this memo provides information for the internet community. Ospf is a standardized linkstate routing protocol, designed to scale efficiently to support larger. Dd2490 p4 2011 ospf is the routing protocol that we deal with in most detail in this course. Ospf route types intraarea route all routes inside an area interarea route routes advertised from one area to another by an area border router external route routes imported into ospf from other protocol or static routes 11 r1 r2 r3 r5 r4 rd ra rc rb ir abrbr asbr to other as ir area 1. The open shortest path first ospf protocol, as its name suggests, is capable of identifying the shortest path to go ahead with the data transfers.
Articulate the leader in rapid elearning and communications. Ospf network type nbma nonbroadcast multiple access uses only unicast communications, so it is the preferred way of ospf configuration in situations where multicast addressing is not possible or desirable for some reasons. The purpose of this lab is to configure ospf on all the devices and test for ping and trace commands. The linkstate based technology was pioneered in arpanet routing protocol 2,3, as compared to the distance vector based routing pro tocol such as rip 11 and bgp 7. 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 a linkstate routing protocol providing fast convergence and excellent scalability. As a linkstate routing protocol it was based on the linkstate algorithm developed for the arpanet in 1980 and the isis routing protocol. Ospf route types intraarea route all routes inside an area interarea route routes advertised from one area to another by an area border router external route routes imported into ospf from other protocol or static routes 11 r1 r2 r3 r5 r4 rd ra rc rb ir abrbr asbr to other as ir area 1 area 0 area 2 area 3. This document is a specification of the open shortest path first ospf tcpip internet routing protocol. Ospf uses database descriptor dbd packets for this purpose. Routing protocol packets are sent with type of service tos of 0. Ospf guide cisco pdf ospf guide cisco pdf ospf guide cisco pdf download.
Hellos, updates and acknowledgments were sent using multicast. Providing information about your neighbor to that neighbor serves as an ack, and proves that communication is bidirectional. Still, the main reason for going into details in ospf is to understand the principles guiding the design of any routing protocol, most principles being general to other routing protocols. Ospf is a link state open standard based routing protocol. Ospf 4, 51 is a link state protocol designed to be used in a single autonomous systemas. Nov 02, 2011 ospf is considered to be an interior gateway protocol which is like isis but unlike ospf isis runs on the datalink layer while ospf runs at layer three the network layer. The router ospf 1 command given in the lab below selects ospf as the routing protocol.
Thats my introduction in to ospf and it is a somewhat complex protocol that needs a complete. Routing protocol packets are sent with type of service tos of. Ospf open shortest path first ospf is defined as open shorted path first protocol and is a dynamic routing protocol. Open shortest path first ospf is a routing protocol for internet protocol ip networks. Verifying the ospf protocol techlibrary juniper networks. The book will also pay the greatest dividends to readers who have used the covered routing protocols in practice, and can connect the highlevel explanations to reallife observed phenomena. Ospf is a common tcpip internal gateway protocol igp used to distribute routing. The open shortest path first ospf protocol, defined in rfc 2328, is an interior gateway protocol used to distribute routing information within. We chose open shortest path first ospf 4 because it is widely used in the internet and it has highquality opensource implementations. 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. To reach our eventual goal of designing a routing protocol purely on ndn, we started with version 1. Since it is based on open standard, we can use it with any vendors router. Ospf uses areas which means you can segment the network more logically. Ospf employs a hierarchical network design using areas.
Ospf is perhaps the most widelyused interior gateway protocol igp in large enterprise networks. Ospf open shortest path first ospf is a standardized linkstate routing protocol, designed to scale efficiently to support larger networks. At start routers are at ospf down state use multicast address 224. Suffered from problems of distance vector protocol count to infinity problem slow convergence large update packets slow response to topological changes need for a link state protocol. Sep 27, 2012 open shortest path first ospf is an adaptive routing protocol for internet protocol ip networks. Open shortest path first ospf is an intradomain routing protocol based on the link state ls algorithm. Routing protocols and architecturesopen shortest path first. Routing protocol is ospf 1 outgoing update filter list for all interfaces is not set incoming update filter list for all interfaces is not set router id 192. Each ospf router maintains an identical database describing the autonomous systems topology. Ospf is link state so it has a better view of the entire network than eigrp before it runs the spf algorithm. According to the author, an understanding of the ospf is crucial to successfully passing the cisco certified internetwork expert ccie exam. Ospf is considered to be a linkstate protocol, unlike rip, ripv2 and igrp, this protocol is what ospf shines on. Ospf was the first widely deployed routing protocol that could converge a network in the low seconds, and guarantee loopfree paths. Ospf neighbor discovery process use ip packet to send hello message.
Ito rin ang pinakasakit na interior gateway routing protocol. An open network operating system designed for efficiency, automation and scale. Ospf was developed as a replacement for the distance vector. Network administrators will usually be more comfortable with ospf because its more commonly deployed. Mar 28, 2015 suffered from problems of distance vector protocol count to infinity problem slow convergence large update packets slow response to topological changes need for a link state protocol. Multicast extensions to ospf mospf version 2 of the open shortest path first ospf routing protocol is defined in rfc1583. Ospf does elect a dr designated router and a bdr backup designated router the drs job is to update all other ospf routers which a called drothers. Ospf protocol defined in rfc 2328, provides a high functionality open protocol that allows multiple vendor networks to communicate using tcpip protocol family. Ospf is a link state routing protocol that is used to distribute information within a single autonomous system.
In 1989, first version of ospf open shortest path first was defined as ospfv1 was published in rfc request for comments 11. Therefore, the neighbor command was not needed for pointtomultipoint interfaces because multicast took care of the traffic. Configuring ospf p1c111 before this feature, some ospf pointtomultipoint protocol traffic was treated as multicast traffic. The second version of ospfv2 open shortest path first version 2 was. Open shortest path first ospf is an adaptive routing protocol for internet protocol ip networks. The working group was formed in 1988 to design an igp based on the shortest path first spf algorithm for use in the internet. Link state routing protocols advertise the state of their links. Overview in lab 6 we discussed rip, which is the canonical example of a routing protocol built on the distancevector algorithm.
It is really advantageous over the rip for certain reasons and we would mention here some of them. Ospf is a complex protocol, more so than many other protocols. For ospf configuration information and examples, refer to the configuring. The hello packet includes linkstate information, as well as a list of neighbors. The ospf protocol is a linkstate routing protocol, which means that the routers exchange. It implements dijkstras algorithm, also known as the shortest path first spf algorithm. This report discusses about the ospf protocol, its advantages, some issues faced while designing large ospf networks. 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. Th synchronization starts as soon as the adjacency is formed between neighbors. Ospf is classified as an interior gateway protocol igp. Open shortest path first ospf is an interior gateway protocol igp standardized by the internet engineering task force ietf and commonly used in large enterprise networks. How to secure a routing protocol remains a chal lenging research issue. Ospf is a linkstate routing protocol with a complex set of options and features. I keep seeing people with network complexity deriving from use of ospf andor as an indirect cause the difficulty or effort of restructuring ospf to accommodate changed design needs.
Ospf is an example of the link state routing protocol. What is open shortest path first ospf definition from. The main advantage of ospf with respect to other intradomain routing protocols is scalability up to some hundreds of routers. Internal gateway protocol igp, routing information protocol rip, variable length subnet masks vlsm introduction. From this database, a routing table is calculated by constructing a shortestpath tree. Ciscos implementation is fully compliant with the specification ospf v2. Five types of ospf routing protocol packets hello packet type 1 database description packet type 2 linkstate request packet type 3 linkstate update packet type 4.
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