IPv4

This document provides guidelines and documents best current practice for operating authoritative DNS servers, recursive resolvers, and stub resolvers in a mixed IPv4/IPv6 environment. This document recommends that both authoritative DNS servers and recursive resolvers support IPv4 and IPv6. It also provides guidance on how recursive DNS resolvers should select upstream DNS servers, including when IPv4-embedded IPv6 addresses are available.

This document obsoletes RFC 3901.

This document defines version 3 of the Virtual Router Redundancy Protocol (VRRP) for IPv4 and IPv6. It obsoletes RFC 5798, which previously specified VRRP (version 3). RFC 5798 obsoleted RFC 3768, which specified VRRP (version 2) for IPv4. VRRP specifies an election protocol that dynamically assigns responsibility for a Virtual Router to one of the VRRP Routers on a LAN. The VRRP Router controlling the IPv4 or IPv6 address(es) associated with a Virtual Router is called the Active Router, and it forwards packets routed to these IPv4 or IPv6 addresses. Active Routers are configured with virtual IPv4 or IPv6 addresses, and Backup Routers infer the address family of the virtual addresses being advertised based on the IP protocol version. Within a VRRP Router, the Virtual Routers in each of the IPv4 and IPv6 address families are independent of one another and always treated as separate Virtual Router instances. The election process provides dynamic failover in the forwarding responsibility should the Active Router become unavailable. For IPv4, the advantage gained from using VRRP is a higher-availability default path without requiring configuration of dynamic routing or router discovery protocols on every end-host. For IPv6, the advantage gained from using VRRP for IPv6 is a quicker switchover to Backup Routers than can be obtained with standard IPv6 Neighbor Discovery mechanisms.

Several IPv6 transition technologies have been developed to provide customers with IPv4-as-a-Service (IPv4aaS) for ISPs with an IPv6-only access and/or core network. These technologies have their advantages and disadvantages. Depending on existing topology, skills, strategy, and other preferences, one of these technologies may be the most appropriate solution for a network operator.

This document examines the five most prominent IPv4aaS technologies and considers a number of different aspects to provide network operators with an easy-to-use reference to assist in selecting the technology that best suits their needs.

This document defines an extension to the Babel routing protocol that allows announcing routes to an IPv4 prefix with an IPv6 next hop, which makes it possible for IPv4 traffic to flow through interfaces that have not been assigned an IPv4 address.

This document specifies a method to find which Registration Data Access Protocol (RDAP) server is authoritative to answer queries for a requested scope, such as domain names, IP addresses, or Autonomous System numbers. This document obsoletes RFC 7484.

This specification defines two Concise Binary Object Representation (CBOR) tags for use with IPv6 and IPv4 addresses and prefixes.

This document specifies new Internet Key Exchange Protocol Version 2 (IKEv2) notification status types to better manage IPv4 and IPv6 coexistence by allowing the responder to signal to the initiator which address families are allowed.

This document updates RFC 7296.

Multiprotocol BGP (MP-BGP) specifies that the set of usable next-hop address families is determined by the Address Family Identifier (AFI) and the Subsequent Address Family Identifier (SAFI). The AFI/SAFI definitions for the IPv4 address family only have provisions for advertising a next-hop address that belongs to the IPv4 protocol when advertising IPv4 Network Layer Reachability Information (NLRI) or VPN-IPv4 NLRI.

This document specifies the extensions necessary to allow the advertising of IPv4 NLRI or VPN-IPv4 NLRI with a next-hop address that belongs to the IPv6 protocol. This comprises an extension of the AFI/SAFI definitions to allow the address of the next hop for IPv4 NLRI or VPN-IPv4 NLRI to also belong to the IPv6 protocol, the encoding of the next hop to determine which of the protocols the address actually belongs to, and a BGP Capability allowing MP-BGP peers to dynamically discover whether they can exchange IPv4 NLRI and VPN-IPv4 NLRI with an IPv6 next hop. This document obsoletes RFC 5549.

When using Traffic Engineering (TE) in a dual-stack IPv4/IPv6 network, the Multiprotocol Label Switching (MPLS) TE Label Switched Path (LSP) infrastructure may be duplicated, even if the destination IPv4 and IPv6 addresses belong to the same remote router. In order to achieve an integrated MPLS TE LSP infrastructure, OSPF routes must be computed over MPLS TE tunnels created using information propagated in another OSPF instance. This issue is solved by advertising cross-address family (X-AF) OSPF TE information.

This document describes an update to RFC 5786 that allows for the easy identification of a router's local X-AF IP addresses.

This document defines YANG modules for the configuration and operation of IPv4-in-IPv6 softwire Border Relays and Customer Premises Equipment for the Lightweight 4over6, Mapping of Address and Port with Encapsulation (MAP-E), and Mapping of Address and Port using Translation (MAP-T) softwire mechanisms.

During the transition to IPv6, there are scenarios where a backbone network internally running one IP address family (referred to as the internal IP or I-IP family) connects client networks running another IP address family (referred to as the external IP or E-IP family). In such cases, the I-IP backbone needs to offer both unicast and multicast transit services to the client E-IP networks.

This document describes a mechanism for supporting multicast across backbone networks where the I-IP and E-IP protocol families differ. The document focuses on the IPv4-over-IPv6 scenario, due to lack of real-world use cases for the IPv6-over-IPv4 scenario.

This document specifies the IPv4 service continuity requirements for IPv6 Customer Edge (CE) routers that are provided either by the service provider or by vendors who sell through the retail market.

Specifically, this document extends the basic requirements for IPv6 CE routers as described in RFC 7084 to allow the provisioning of IPv6 transition services for the support of IPv4-as-a-Service (IPv4aaS) by means of new transition mechanisms. The document only covers IPv4aaS, i.e., transition technologies for delivering IPv4 in IPv6-only access networks. IPv4aaS is necessary because there aren't sufficient IPv4 addresses available for every possible customer/ device. However, devices or applications in the customer Local Area Networks (LANs) may be IPv4-only or IPv6-only and still need to communicate with IPv4-only services on the Internet.