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OSPF Version 2 (RFC2178)

IP.com Disclosure Number: IPCOM000002736D
Original Publication Date: 1997-Jul-01
Included in the Prior Art Database: 2019-Feb-15

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Moy: AUTHOR

Related Documents

10.17487/RFC2178: DOI

Abstract

This memo documents version 2 of the OSPF protocol. OSPF is a link-state routing protocol. It is designed to be run internal to a single Autonomous System. Each OSPF router maintains an identical database describing the Autonomous System's topology. From this database, a routing table is calculated by constructing a shortest-path tree. OSPF recalculates routes quickly in the face of topological changes, utilizing a minimum of routing protocol traffic. OSPF provides support for equal-cost multipath. An area routing capability is provided, enabling an additional level of routing protection and a reduction in routing protocol traffic. In addition, all OSPF routing protocol exchanges are authenticated. [STANDARDS-TRACK]

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Network Working Group J. Moy Request for Comments: 2178 Cascade Communications Corp. Obsoletes: 1583 July 1997 Category: 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. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Abstract

This memo documents version 2 of the OSPF protocol. OSPF is a link- state routing protocol. It is designed to be run internal to a single Autonomous System. Each OSPF router maintains an identical database describing the Autonomous System’s topology. From this database, a routing table is calculated by constructing a shortest- path tree.

OSPF recalculates routes quickly in the face of topological changes, utilizing a minimum of routing protocol traffic. OSPF provides support for equal-cost multipath. An area routing capability is provided, enabling an additional level of routing protection and a reduction in routing protocol traffic. In addition, all OSPF routing protocol exchanges are authenticated.

The differences between this memo and RFC 1583 are explained in Appendix G. All differences are backward-compatible in nature. Implementations of this memo and of RFC 1583 will interoperate.

Please send comments to ospf@gated.cornell.edu.

Table of Contents

1 Introduction ........................................... 5 1.1 Protocol Overview ...................................... 5 1.2 Definitions of commonly used terms ..................... 6 1.3 Brief history of link-state routing technology ........ 9 1.4 Organization of this document ......................... 10 1.5 Acknowledgments ....................................... 11 2 The link-state database: organization and calculations 11 2.1 Representation of routers and networks ................ 11

Moy Standards Track [Page 1]

RFC 2178 OSPF Version 2 July 1997

2.1.1 Representation of non-broadcast networks .............. 13 2.1.2 An example link-state database ........................ 14 2.2 The shortest-path tree ................................ 18 2.3 Use of external routing information ................... 20 2.4 Equal-cost multipath .................................. 22 3 Splitting the AS into Areas ........................... 22 3.1 The backbone of the Autonomous System ................. 23 3.2 Inter-area routing .................................... 23 3.3 Classification of routers ............................. 24 3.4 A sample area configuration ........................... 25 3.5 IP subnetting support ................................. 31 3.6 Supporting stub areas ................................. 32 3.7 Partitions of areas ................................... 33 4 Functional Summary .................................... 34 4.1 Inter-area routing .................................... 35 4.2 AS...

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