OSPF Stub Router Advertisement
RFC 6987

• Status
• IESG evaluation record
• IESG writeups
• Email expansions
• History

• Versions
• 00
• 01
• 02
• 03
• 04

Internet Engineering Task Force (IETF)                         A. Retana
Request for Comments: 6987                                     L. Nguyen
Obsoletes: 3137                                      Cisco Systems, Inc.
Category: Informational                                         A. Zinin
ISSN: 2070-1721                                          Cinarra Systems
                                                                R. White

                                                            D. McPherson
                                                          Verisign, Inc.
                                                          September 2013

                     OSPF Stub Router Advertisement

Abstract

   This document describes a backward-compatible technique that may be
   used by OSPF (Open Shortest Path First) implementations to advertise
   a router's unavailability to forward transit traffic or to lower the
   preference level for the paths through such a router.

   This document obsoletes RFC 3137.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6987.

Retana, et al.                Informational                     [Page 1]
RFC 6987             OSPF Stub Router Advertisement       September 2013

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Solutions . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  OSPFv3-Only Solution  . . . . . . . . . . . . . . . . . .   3
   3.  Maximum Link Metric . . . . . . . . . . . . . . . . . . . . .   4
   4.  Deployment Considerations . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Changes from RFC 3137  . . . . . . . . . . . . . . .   6

1.  Introduction

   In some situations, it may be advantageous to inform routers in a
   network not to use a specific router as a transit point but to still
   route to it.  Possible situations include the following:

   o  The router is in a critical condition (for example, has a very
      high CPU load or does not have enough memory to store all Link
      State Advertisements (LSAs) or build the routing table).

   o  Graceful introduction and removal of the router to/from the
      network.

   o  Other (administrative or traffic engineering) reasons.

Retana, et al.                Informational                     [Page 2]
RFC 6987             OSPF Stub Router Advertisement       September 2013

   Note that the solution introduced in this document does not remove
   the router from the topology view of the network (as could be done by
   just flushing that router's router-LSA) but discourages other routers
   from using it for transit routing, while still routing packets to the
   router's own IP addresses, i.e., the router is announced as a stub.

   It must be emphasized that the solution provides real benefits in
   networks designed with at least some level of redundancy, so that
   traffic can be routed around the stub router.  Otherwise, traffic
   destined for the networks and reachable through such a stub router
   may still be routed through it.

2.  Solutions

   The solution introduced in this document solves two challenges
   associated with the outlined problem.  In the description below,
   router X is the router announcing itself as a stub.  The challenges