Virtual Subnet: A BGP/MPLS IP VPN-Based Subnet Extension Solution
RFC 7814

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Internet Engineering Task Force (IETF)                             X. Xu
Request for Comments: 7814                           Huawei Technologies
Category: Informational                                     C. Jacquenet
ISSN: 2070-1721                                                   Orange
                                                               R. Raszuk
                                                                T. Boyes
                                                            Bloomberg LP
                                                                  B. Fee
                                                        Extreme Networks
                                                              March 2016

   Virtual Subnet: A BGP/MPLS IP VPN-Based Subnet Extension Solution

Abstract

   This document describes a BGP/MPLS IP VPN-based subnet extension
   solution referred to as "Virtual Subnet", which can be used for
   building Layer 3 network virtualization overlays within and/or
   between data centers.

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/rfc7814.

Xu, et al.                    Informational                     [Page 1]
RFC 7814                     Virtual Subnet                   March 2016

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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Solution Description  . . . . . . . . . . . . . . . . . . . .   5
     3.1.  Unicast . . . . . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Intra-subnet Unicast  . . . . . . . . . . . . . . . .   5
       3.1.2.  Inter-subnet Unicast  . . . . . . . . . . . . . . . .   6
     3.2.  Multicast . . . . . . . . . . . . . . . . . . . . . . . .   8
     3.3.  Host Discovery  . . . . . . . . . . . . . . . . . . . . .   9
     3.4.  ARP/ND Proxy  . . . . . . . . . . . . . . . . . . . . . .   9
     3.5.  Host Mobility . . . . . . . . . . . . . . . . . . . . . .   9
     3.6.  Forwarding Table Scalability on Data-Center Switches  . .  10
     3.7.  ARP/ND Cache Table Scalability on Default Gateways  . . .  10
     3.8.  ARP/ND and Unknown Unicast Flood Avoidance  . . . . . . .  10
     3.9.  Path Optimization . . . . . . . . . . . . . . . . . . . .  10
   4.  Limitations . . . . . . . . . . . . . . . . . . . . . . . . .  11
     4.1.  Non-support of Non-IP Traffic . . . . . . . . . . . . . .  11
     4.2.  Non-support of IP Broadcast and Link-Local Multicast  . .  11
     4.3.  TTL and Traceroute  . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  12
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  12
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

Xu, et al.                    Informational                     [Page 2]
RFC 7814                     Virtual Subnet                   March 2016

1.  Introduction

   For business continuity purposes, Virtual Machine (VM) migration
   across data centers is commonly used in situations such as data-
   center maintenance, migration, consolidation, expansion, or disaster
   avoidance.  The IETF community has recognized that IP renumbering of
   servers (i.e., VMs) after the migration is usually complex and
   costly.  To allow the migration of a VM from one data center to
   another without IP renumbering, the subnet on which the VM resides