Using Conditional Router Advertisements for Enterprise Multihoming
RFC 8475
Internet Engineering Task Force (IETF) J. Linkova
Request for Comments: 8475 Google
Category: Informational M. Stucchi
ISSN: 2070-1721 RIPE NCC
October 2018
Using Conditional Router Advertisements for Enterprise Multihoming
Abstract
This document discusses the most common scenarios of connecting an
enterprise network to multiple ISPs using an address space assigned
by an ISP and how the approach proposed in "Enterprise Multihoming
using Provider-Assigned Addresses without Network Prefix Translation:
Requirements and Solution" could be applied in those scenarios. The
problem of enterprise multihoming without address translation of any
form has not been solved yet as it requires both the network to
select the correct egress ISP based on the packet source address and
hosts to select the correct source address based on the desired
egress ISP for that traffic. The aforementioned document proposes a
solution to this problem by introducing a new routing functionality
(Source Address Dependent Routing) to solve the uplink selection
issue. It also proposes using Router Advertisements to influence the
host source address selection. It focuses on solving the general
problem and covering various complex use cases, and this document
adopts its proposed approach to provide a solution for a limited
number of common use cases. In particular, the focus of this
document is on scenarios in which an enterprise network has two
Internet uplinks used either in primary/backup mode or simultaneously
and hosts in that network might not yet properly support multihoming
as described in RFC 8028.
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/rfc8475.
Linkova & Stucchi Informational [Page 1]
RFC 8475 Conditional RAs October 2018
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Common Enterprise Multihoming Scenarios . . . . . . . . . . . 4
2.1. Two ISP Uplinks, Primary and Backup . . . . . . . . . . . 4
2.2. Two ISP Uplinks, Used for Load-Balancing . . . . . . . . 5
3. Conditional Router Advertisements . . . . . . . . . . . . . . 5
3.1. Solution Overview . . . . . . . . . . . . . . . . . . . . 5
3.1.1. Uplink Selection . . . . . . . . . . . . . . . . . . 5
3.1.2. Source Address Selection and Conditional RAs . . . . 5
3.2. Example Scenarios . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Single Router, Primary/Backup Uplinks . . . . . . . . 8
3.2.2. Two Routers, Primary/Backup Uplinks . . . . . . . . . 9
3.2.3. Single Router, Load-Balancing between Uplinks . . . . 12
3.2.4. Two Routers, Load-Balancing between Uplinks . . . . . 12
3.2.5. Topologies with Dedicated Border Routers . . . . . . 13
3.2.6. Intrasite Communication during Simultaneous Uplinks
Outage . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.7. Uplink Damping . . . . . . . . . . . . . . . . . . . 15
3.2.8. Routing Packets When the Corresponding Uplink Is
Unavailable . . . . . . . . . . . . . . . . . . . . . 16
3.3. Solution Limitations . . . . . . . . . . . . . . . . . . 16
3.3.1. Connections Preservation . . . . . . . . . . . . . . 17
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