OSPF Version 2
RFC 2178
| Document | Type |
RFC - Draft Standard
(July 1997; No errata)
Obsoleted by RFC 2328
Obsoletes RFC 1583
|
|
|---|---|---|---|
| Last updated | 2013-03-02 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 2178 (Draft Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | (None) | ||
| Send notices to | (None) | ||
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 external routes .................................... 35
4.3 Routing protocol packets .............................. 35
4.4 Basic implementation requirements ..................... 38
4.5 Optional OSPF capabilities ............................ 39
5 Protocol data structures .............................. 40
6 The Area Data Structure ............................... 42
7 Bringing Up Adjacencies ............................... 44
7.1 The Hello Protocol .................................... 44
7.2 The Synchronization of Databases ...................... 45
7.3 The Designated Router ................................. 46
7.4 The Backup Designated Router .......................... 47
7.5 The graph of adjacencies .............................. 48
8 Protocol Packet Processing ............................ 49
8.1 Sending protocol packets .............................. 49
8.2 Receiving protocol packets ............................ 51
9 The Interface Data Structure .......................... 54
9.1 Interface states ...................................... 57
9.2 Events causing interface state changes ................ 59
9.3 The Interface state machine ........................... 61
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