RFC 1587 (rfc1587) - Page 1 of 17

The OSPF NSSA Option

Network Working Group                                          R. Coltun
Request for Comments: 1587                  RainbowBridge Communications
Category: Standards Track                                      V. Fuller
                                                     Stanford University
                                                              March 1994


                          The OSPF NSSA Option

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.

Table Of Contents

   1.0 Abstract .................................................  1
   2.0 Overview .................................................  2
   2.1 Motivation ...............................................  2
   2.2 Proposed Solution ........................................  3
   3.0 Implementation Details ...................................  5
   3.1 The N-bit ................................................  5
   3.2 Type-7 Address Ranges ....................................  5
   3.3 Type-7 LSAs ..............................................  5
   3.4 Originating Type-7 LSAs ..................................  7
   3.5 Calculating Type-7 AS External Routes ....................  8
   3.6 Incremental Updates ...................................... 10
   4.0 Originating Type-5 LSAs .................................. 10
   4.1 Translating Type-7 LSAs .................................. 10
   4.2 Flushing Translated Type-7 LSAs .......................... 13
   5.0 Acknowledgements ......................................... 13
   6.0 References ............................................... 13
   7.0 Security Considerations .................................. 13
   8.0 Authors' Addresses ....................................... 14
   Appendix A: Type-7 LSA Packet Format ......................... 15
   Appendix B: The Options Field ................................ 16
   Appendix C: Configuration Parameters ......................... 17

1.0  Abstract

   This document describes a new optional type of OSPF area, somewhat
   humorously referred to as a "not-so-stubby" area (or NSSA).  NSSAs
   are similar to the existing OSPF stub area configuration option but
   have the additional capability of importing AS external routes in a
   limited fashion.



Coltun & Fuller