Internet-Draft EVPN Next Hop address encoding September 2022
Dubrovsky Expires 7 March 2023 [Page]
Internet Engineering Task Force
7432 (if approved)
Intended Status:
Standards Track
M. Dubrovsky

EVPN Next Hop address encoding


This document clarifies that the EVPN route Next Hop encoding is unaffected by whether the underlying BGP session is IPv4 or IPv6.

From that perspective, this document updates the EVPN specification to provide more comprehensive documentation of the encoding.

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

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This Internet-Draft will expire on 7 March 2023.

Table of Contents

1. Introduction

For operational simplicity, a network administrator can choose to enable multiple AFI/SAFI over a single BGP session.

While [RFC7432] specifies that the Next Hop field of the MP_REACH_NLRI attribute can be set to the IPv4 or IPv6 address for EVPN routes, it does not clarify the exact encoding when the address family of a BGP session does not match the address family of the EVPN Next Hop address.

For the sake of interoperability, this document specifies the encoding and therefore, updates [RFC7432]. EVPN implementations MUST conform to the prescribed encoding.

2. Requirements Language

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. EVPN MP_REACH_NLRI Next Hop encoding

EVPN MP_REACH_NLRI can be advertised with either IPv4 or IPv6 next hop.

EVPN MP_REACH_NLRI IPv4 Next Hop encoding:

Table 1: EVPN MP_REACH_NLRI IPv4 next Hop encoding
Length of Next Hop Address = 4
Network Address of Next Hop = IPv4 address

EVPN MP_REACH_NLRI IPv6 next Hop encoding:

Table 2: EVPN MP_REACH_NLRI IPv6 next Hop encoding
Length of Next Hop Address = 16
Network Address of Next Hop = IPv6 address

The above encoding is done regardless of whether the BGP session is running over IPv4 or IPv6.

4. IANA Considerations

This memo includes no request to IANA.

5. Security Considerations

This document should not affect the security of the Internet.

6. References

6.1. Normative References

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, , <>.


The author would like to thank Aamod Vyavaharkar and Kyuhwan Kim for their helpful feedback.

Author's Address

Mike Dubrovsky