OSPF Version 2 (RFC1247)
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Oct-24
Internet Society Requests For Comment (RFCs)
This memo documents version 2 of the OSPF protocol. OSPF is a link- state based 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. (Download file contains alternative document formats.)
Network Working Group J. Moy
Request for Comments: 1247 Proteon, Inc.
Obsoletes: RFC 1131 July 1991
OSPF Version 2
Status of this Memo
This RFC specifies an IAB standards track protocol for the Internet
community, and requests discussion and suggestions for improvements.
Please refer to the current edition of the ``IAB Official Protocol
Standards'' for the standardization state and status of this protocol.
Distribution of this memo is unlimited.
This memo documents version 2 of the OSPF protocol. OSPF is a link-
state based 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
OSPF recalculates routes quickly in the face of topological changes,
utilizing a minimum of routing protocol traffic. OSPF provides support
for equal-cost multipath. Separate routes can be calculated for each IP
type of service. 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
Version 1 of the OSPF protocol was documented in RFC 1131. The
differences between the two versions are explained in Appendix F.
Please send comments to email@example.com.
This document is a specification of the Open Shortest Path First (OSPF)
internet routing protocol. OSPF is classified as an Internal Gateway
Protocol (IGP). This means that it distributes routing information
between routers belonging to a single Autonomous System. The OSPF
protocol is based on SPF or link-state technology. This is a departure
[Moy] [Page 1]
RFC 1247 OSPF Version 2 July 1991
from the Bellman-Ford base used by traditional internet routing
The OSPF protocol was developed by the OSPF working group of the
Internet Engineering Task Force. It has been designed expressly for the
internet environment, including explicit support for IP subnetting,
TOS-based routing and the tagging of externally-derived routing
information. OSPF also provides for the authentication of routing
updates, and utilizes IP multicast when sending/receiving the updates.
In addition, much work has been done to produce a protocol that responds
quickly to topology changes, yet involves small amounts of routing
The author would like to thank Rob Coltun, Milo Medin, Mike Petry and
the rest of the OSPF working group for the ideas and support they have
given to this project.
1.1 Protocol overview
OSPF routes IP packets based solely on the destination IP address and IP
Type of Service found in the IP packet header. IP packets are routed
"as is" -- they are not encapsulated in any further protocol headers as
they transit the Autonomous System. OSPF is a dynamic routing protocol.
It quickly detects topological changes in the AS (such as route...