Solutions for BGP Persistent Route Oscillation
RFC 7964
Internet Engineering Task Force (IETF) D. Walton
Request for Comments: 7964 Cumulus Networks
Category: Standards Track A. Retana
ISSN: 2070-1721 E. Chen
Cisco Systems, Inc.
J. Scudder
Juniper Networks
September 2016
Solutions for BGP Persistent Route Oscillation
Abstract
Routing information reduction by BGP Route Reflection or
Confederation can result in persistent internal BGP route
oscillations with certain routing setups and network topologies.
This document specifies two sets of additional paths that can be used
to eliminate these route oscillations in a network.
Status of This Memo
This is an Internet Standards Track document.
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). Further information on
Internet Standards is available in Section 2 of RFC 7841.
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/rfc7964.
Copyright Notice
Copyright (c) 2016 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.
Walton, et al. Standards Track [Page 1]
RFC 7964 BGP Oscillation Solutions September 2016
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Advertise All the Available Paths . . . . . . . . . . . . . . 3
4. Advertise the Group Best Paths . . . . . . . . . . . . . . . 3
5. Route Reflection and Confederation . . . . . . . . . . . . . 4
5.1. Route Reflection . . . . . . . . . . . . . . . . . . . . 5
5.2. Confederation . . . . . . . . . . . . . . . . . . . . . . 5
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. Why the Group Best Paths Are Adequate . . . . . . . 8
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
As documented in [RFC3345], routing information reduction by BGP
Route Reflection [RFC4456] or BGP Confederation [RFC5065] can result
in persistent Internal BGP (IBGP) route oscillations with certain
routing setups and network topologies. Except for a couple of
artificially engineered network topologies, the MULTI_EXIT_DISC (MED)
attribute [RFC4271] has played a pivotal role in virtually all known
persistent IBGP route oscillations. For the sake of brevity, we use
the term "MED-induced route oscillation" hereafter to refer to a
persistent IBGP route oscillation in which the MED plays a role.
In order to eliminate MED-induced route oscillations and to achieve
consistent routing in a network, a route reflector or a confederation
Autonomous System Border Router (ASBR) needs to advertise more than
just the best path for an address prefix. Our goal is to identify
the necessary set of paths for an address prefix that needs to be
advertised by a route reflector or a confederation ASBR to prevent
the condition.
In this document, we describe two sets of paths for an address prefix
that can be advertised by a BGP route reflector or confederation ASBR
to eliminate MED-induced route oscillations in a network. The first
set involves all the available paths, and would achieve the same
routing consistency as the full IBGP mesh. The second set, which is
a subset of the first one, involves the neighbor-AS-based Group Best
Show full document text