Hop count is the only metrics to describe the best path to a remote network, but it can be 15 at max. I did a debug ip ospf event on one router and saw the following. This means that junos os maintains a single best route to an autonomous system as boundary router in the ospf routing table, rather than multiple intraas paths, if they are available. Ospf is a common tcpip internal gateway protocol igp used to distribute routing. Rfc 1583 specifies a different method than rfc 2328 for selecting an external route from multiple lsas.
Rfc 2328 ospf version 2 april 1998 router generates an lsa for the network and has other special responsibilities in the running of the protocol. The mask indicates the number of nodes on the network. Ospf 7 ospf open shortest path first ospf is a dynamic routing protocol based on the link state algorithm. Implementations of rfc 1247 and of this memo will interoperate. Rfc 1584 provides extensions to ospf for the support of ip multicast traffic. The differences between this memo and rfc 1583 are explained in appendix g. Open shortest path first ospf is a linkstate igp developed by the ospf working group of the ietf. Company a has bought company b and must merge its network into its own. Rfc 1583 ospf version 2 march 1994 directed graph as a stub connection. Ospf and isis are blessed as equals by ietf, with ospf somewhat more equal zprivate cooperation improves both protocols 1990 zdualmode isis rfc published isis becomes iso proposed standard private cooperation improves both protocols. Rfc 1584 multicast extensions to ospf march 1994 sourcedestination routing, this is in contrast to most unicast datagram forwarding algorithms like ospf that route based solely on destination. View and download brocade communications systems fastiron x series software update online. This used to be w bit for mospf and has been reclaimed in the latest ospfv3 rfc router interface information may be spread across multiple router lsas. All vendors have since based their implementations of ospf on rfc 2328.
This report discusses about the ospf protocol, its advantages, some issues faced while designing large ospf networks. Rfc 2328 ospf version 2 rfc 2740 ospf version 3 rfc 11 describes the first iteration of ospf and it was used in initial tests to determine whether the protocol worked. Tcpip environment fast convergence variablelength subnet masks discontiguous subnets incremental updates. The designated router concept enables a reduction in the number of. 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. Once you are in the router ospf configuration submode, configure the lan network 172. It is defined as ospf version 2 in rfc 2328 1998 for ipv4. Please watch eigrp routing protocol 1, you will understand more. Ospf is classified as an interior gateway protocol igp. In this update i will explore how to merge an existing ospf network with an existing eigrp network and also touch on some other subjects which you can read about in the objectives below.
Ospf version 2 was originally documented in rfc 1247. Internal gateway protocol igp, routing information protocol rip, variable length subnet masks vlsm introduction. This is from rfc 3101, when set, the router is an nssa abr bit x. The difference between rfc 1583 and rfc 2328, in regard to how to choose the best route among multiple external routes, is discussed in this section. Ospf hierarchical ospf howinside areas full ospfflooding is limited to areasarea border routers summarize information. Ospf open shortest path first link state or spf technology developed by ospf working group of ietf rfc 1247 ospfv2 ipv4 standard described in rfc2328 ospfv3 ipv6 standard described in rfc2740 designed for. The updates for ipv6 are specified as ospf version 3 in rfc 5340 2008. The difference between rfc 1583 and rfc 2328, in regard to how. The differences between rfc 1247 and this memo are explained in appendix e.
Figure 23 hitless stacking support during a stack merge fcx stack merge stack 1 active 1 pri30 standby 2 pri20 member 3 pri10 member 4 pri0 stack 2 active 1 pri100 standby 2 pri50 1 1 member 1 pri30 member 2 pri20 member 3 pri10 member 4 pri0 active 5 pri100 standby 6 pri50 1 when hitless failover is enabled. In every 30 seconds, it delivers an entire routing table to all active interfaces. 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. By default, the junos os implementation of ospf is compatible with rfc 1583. Ospf open shortest path first link state or spf technology developed by ospf working group of ietf rfc 1247 designed for tcpip internet environment fast convergence variablelength subnet masks discontiguous subnets no periodic updates route authentication. In ospf, the source and destination of a routing protocol packet are the two ends of an potential adjacency. However nxos supports rfc 2328 and there are designs wherein this. Rfc 1253 ospf version 2 management information base. This task enables rfc 2328 to be compatible with rfc 1583. Lsasummaryarea 0 backbone mandatoryinterarea communication only through area 0no loops allowed among areasonly 2 levels hierarchy allowed 17 10.
Merging two ospf networks together be it via a virtual link or directly merging the area 0s requires complete understanding of the two ospf ases. Standards track ospf version 2 status of this memo this document specifies an internet standards track protocol for the internet community, and requests discussion and suggestions for improvements. Tcpip environment fast convergence variablelength subnet masks. Rfc 1583 ospf version 2 march 1994 broadcast networks networks supporting many more than two attached routers, together with the capability to address a single physical message to all of the attached routers broadcast. Shah ciena february 2018 ospf traffic engineering ospfte link availability extension for links with variable discrete bandwidth abstract a network may contain links with variable. The differences consist of bug fixes and clarifications, and are backwardcompatible in nature. Standards track april 1995 extending ospf to support demand circuits status of this memo this document specifies an internet standards track protocol for the internet community, and requests discussion and suggestions for improvements. An area routing capability is provided, enabling an additional level of routing protection and a reduction in routing protocol traffic. To help illustrate better how the ospf messages are used, its worth taking a quick look at the format used for each of these messages. There will be a new section discussing premature aging section 14.
Ospf is a complex protocol, more so than many other protocols. This memo documents version 2 of the ospf protocol. Multitopology mt routing in ospf status of this memo this document specifies an internet standards track protocol for the internet community, and requests discussion and suggestions for improvements. Rfc 1587 and rfc 1583 compatibility with ospfv3 address family. By default, the junos os implementation of ospfv2 is compatible with rfc 1583, ospf version 2. Each network stub or transit in the graph has an ip address and associated network mask. Difference between rip and ospf with comparison chart. Information protocol rip version 1 rfc 1058 and rip version 2 rfc 1723. However nxos supports rfc 2328 and there are designs wherein this difference can create routing loops in the network when there are external ospf routes in the network. Rfc 1583 ospf version 2 march 1994 packet length the length of the protocol packet in bytes. This means that it distributes routing information between routers belonging to a single autonomous system. Hosts attached directly to routers referred to as host routes appear on the graph as stub networks. The significant metric in ospf is the ospf costs, which is calculated from the available bit rate of a link. The designated router is elected by the hello protocol.
Still, the main reason for going into details in ospf is to. Coltun computer science center august 1991 ospf version 2 management information base status of this memo this rfc specifies an iab standards track protocol for the internet community, and requests discussion and suggestions for improvements. Rfc 11 ospf october 1989 e authentication all ospf protocol exchanges are authenticated. Network working group internet architecture board request for comments. 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. Moy standards track page 1 rfc 2328 ospf version 2 april 1998 implementations of this memo and of rfcs 2178, 1583, and 1247 will interoperate. Introduction this document is a specification of the open shortest path first ospf tcpip internet routing protocol. This is commonly referred to as multicast ospf mospf. Rfc 1793 extending ospf to support demand circuits rfc1793.
Fastiron sx 800, icx 6610 series, icx 6430 series, icx 6450 series, icx 6650 series, fastiron sx 1600, fcx series. Receivers must concatenate all the routerlsas originated by a given router when running the spf calculation. It prevents routing loops, through restricting the number of hop counts permitted in. This paper examines how ospf works and how it can be used to design and build todays large and complicated networks.
Overview in lab 6 we discussed rip, which is the canonical example of a routing protocol built on the distancevector algorithm. Ospf message formats page 1 of 7 ospf uses five different types of messages to communicate both linkstate and general information between routers within an autonomous system or area. 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. Rfc 1587 and rfc 1583 compatibility with ospfv3 address family 1configure ospfv3 address families for both ipv4 ipv6. Routing information protocol is the straight implementation of distance vector routing for local networks. The ospf network command uses a combination of networkaddress and wildcardmask. Ospf routing loopsuboptimal routing between cisco ios. Please refer to the current edition of the internet official protocol standards std 1 for the standardization state and status of this protocol.
Rfc 1247 ospf version 2 july 1991 of the advertisement must be originated due either to topological change of the expiration of the ls refresh timer the current instance must. In addition, all ospf routing protocol exchanges are authenticated. The working group was formed in 1988 to design an igp based on the. Understand the basics of ospf routing protocol with lab and packet captures setup gns3. I would no recommend using virtual links as virtual links are resigned to connect an ospf area to area 0 via another area. This algorithm is based on the link states between the routers involved.
The differences between this memo and rfc 2178 are explained in appendix g. Rfc 5709, rfc 6549, rfc 6845, rfc 6860, rfc 7474, rfc 8042 author. Ospf linkstate routing and open shortest path first olof hagsand kth csc dd2490 p4 2011 ospf is the routing protocol that we deal with in most detail in this course. The 16bit ones complement of the ones complement sum of the entire contents of the packet, starting with the ospf packet header, and prepending a pseudoheader of ipv6 header fields. 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. View errata submit errata find ipr disclosures from the ietf. Ospf mib support of rfc 1850 and latest extensions.