Internet-Draft IPv6-Resolved IPv4 Gateway October 2025
Mook Expires 23 April 2026 [Page]
Workgroup:
Network Working Group
Internet-Draft:
draft-ipv6-resolved-gateway-00
Published:
Intended Status:
Informational
Expires:
Author:
R. V. Mook
Asteroid International B.V.

IPv6-Resolved IPv4 Gateway

Abstract

This document requests the allocation of a new IPv4 special-purpose address from the IANA IPv4 Special-Purpose Address Registry. The proposed address, 192.0.0.11/32, is intended to serve as a signal to IPv4 hosts in IPv6-only networks that the link-layer resolution for the default gateway should be derived from the IPv6 default gateway learned via IPv6 Router Advertisements and Neighbor Discovery.

This approach enables IPv4 communication without requiring IPv4 subnets or the use of ARP. It maintains backward compatibility with existing IPv4 host software that expects a default gateway IP address, while avoiding the need to implement legacy link-layer protocols.

About This Document

This note is to be removed before publishing as an RFC.

Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ipv6-resolved-gateway/.

Source for this draft and an issue tracker can be found at https://github.com/remcovanmook/draft-ipv6-resolved-gateway.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

This Internet-Draft will expire on 23 April 2026.

Table of Contents

1. Introduction

In IPv6-only infrastructure environments, such as modern data centers and ISP networks, IPv4 communication may still be required by applications or systems. However, traditional IPv4 mechanisms like ARP and subnet configuration impose unnecessary complexity in such environments.

Hosts in these environments typically receive IPv6 configuration through SLAAC or DHCPv6, including a default gateway. This document proposes a method by which IPv4 traffic may also be sent without requiring ARP or an IPv4 subnet: by configuring a well-known IPv4 address (192.0.0.11) as the default gateway, and resolving its link-layer address using the IPv6 default gateway learned by the host.

2. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. Rationale

The key goal is to enable IPv4 communication in environments that are natively IPv6-only, without relying on dual-stack or tunneling. This is accomplished by decoupling IPv4 next-hop resolution from ARP and instead aligning it with the IPv6 default gateway.

By defining 192.0.0.11 as a special-purpose IPv4 address, hosts can be configured with IPv4 /32 addresses and this default gateway, eliminating the need for any IPv4 subnet or address resolution mechanisms.

4. Host Behavior and Next-Hop Resolution

When a host is configured to use 192.0.0.11 as its IPv4 default gateway, the host's operating system should implement the following logic:

5. Compatibility Considerations

6. Security Considerations

This approach reduces ARP-related attack surfaces by removing ARP from the network. It assumes integrity of IPv6 neighbor discovery, and any associated risks (e.g., spoofed RAs) are equivalent to standard IPv6 host risks.

Additionally, subnet scanning attacks against IPv4 networks are mitigated, since hosts are only configured with /32 addresses and ARP is not available to discover neighbors.

7. IANA Considerations

This document requests the following addition to the IANA IPv4 Special-Purpose Address Registry:

Address Block: 192.0.0.11/32 Name: IPv6-Resolved Default Gateway RFC: [This document] Allocation Date: [to be assigned] Termination Date: N/A Source: False Destination: True Forwardable: True Global: No Reserved-by-Protocol: No

8. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/rfc/rfc2119>.
[RFC4861]
"Neighbor Discovery for IP version 6 (IPv6)", n.d..
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC8200]
"Internet Protocol, Version 6 (IPv6) Specification", n.d..

Acknowledgments

The author would like to thank Tobias Fiebig and Warren Kumari for their input on this document.

Author's Address

Remco van Mook
Asteroid International B.V.