Enterprise Multihoming using Provider-Assigned IPv6 Addresses without Network Prefix Translation: Requirements and Solutions
RFC 8678
Internet Engineering Task Force (IETF) F. Baker
Request for Comments: 8678
Category: Informational C. Bowers
ISSN: 2070-1721 Juniper Networks
J. Linkova
Google
December 2019
Enterprise Multihoming Using Provider-Assigned IPv6 Addresses without
Network Prefix Translation: Requirements and Solutions
Abstract
Connecting an enterprise site to multiple ISPs over IPv6 using
provider-assigned addresses is difficult without the use of some form
of Network Address Translation (NAT). Much has been written on this
topic over the last 10 to 15 years, but it still remains a problem
without a clearly defined or widely implemented solution. Any
multihoming solution without NAT requires hosts at the site to have
addresses from each ISP and to select the egress ISP by selecting a
source address for outgoing packets. It also requires routers at the
site to take into account those source addresses when forwarding
packets out towards the ISPs.
This document examines currently available mechanisms for providing a
solution to this problem for a broad range of enterprise topologies.
It covers the behavior of routers to forward traffic by taking into
account source address, and it covers the behavior of hosts to select
appropriate default source addresses. It also covers any possible
role that routers might play in providing information to hosts to
help them select appropriate source addresses. In the process of
exploring potential solutions, this document also makes explicit
requirements for how the solution would be expected to behave from
the perspective of an enterprise site network administrator.
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 candidates for any level of Internet
Standard; see 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
https://www.rfc-editor.org/info/rfc8678.
Copyright Notice
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Table of Contents
1. Introduction
2. Requirements Language
3. Terminology
4. Enterprise Multihoming Use Cases
4.1. Simple ISP Connectivity with Connected SERs
4.2. Simple ISP Connectivity Where SERs Are Not Directly
Connected
4.3. Enterprise Network Operator Expectations
4.4. More Complex ISP Connectivity
4.5. ISPs and Provider-Assigned Prefixes
4.6. Simplified Topologies
5. Generating Source-Prefix-Scoped Forwarding Tables
6. Mechanisms for Hosts To Choose Good Default Source Addresses in
a Multihomed Site
6.1. Default Source Address Selection Algorithm on Hosts
6.2. Selecting Default Source Address When Both Uplinks Are
Working
6.2.1. Distributing Default Address Selection Policy
Table with DHCPv6
6.2.2. Controlling Default Source Address Selection with
Router Advertisements
6.2.3. Controlling Default Source Address Selection with
ICMPv6
6.2.4. Summary of Methods for Controlling Default Source
Address Selection to Implement Routing Policy
6.3. Selecting Default Source Address When One Uplink Has Failed
6.3.1. Controlling Default Source Address Selection with
DHCPv6
6.3.2. Controlling Default Source Address Selection with
Router Advertisements
6.3.3. Controlling Default Source Address Selection with
ICMPv6
6.3.4. Summary of Methods for Controlling Default Source
Address Selection on the Failure of an Uplink
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