RFC 6515, "IPv4 and IPv6 Infrastructure Addresses in BGP Updates for Multicast VPN", February 2012

Errata ID: 5738
Status: Rejected
Type: Technical
Publication Format(s) : TEXT
Reported By: Jingrong Xie
Date Reported: 2019-05-25
Rejected by: Martin Vigourex
Date Rejected: 2021-02-08

Section 2 says:

   1. "Network Address of Next Hop" field in the MP_REACH_NLRI
      attribute, as defined in Section 3 of [BGP-MP].  This field is
      preceded by a "length of next hop address" field. Hence, it is
      always clear whether the address is an IPv4 address (length is 4)
      or an IPv6 address (length is 16).  If the length of the next hop
      address is neither 4 nor 16, the MP_REACH_NLRI attribute MUST be
      considered to be "incorrect", and MUST be handled as specified in
      Section 7 of [BGP-MP].

It should say:

   1. "Network Address of Next Hop" field in the MP_REACH_NLRI
      attribute, as defined in Section 3 of [BGP-MP].  This field is
      preceded by a "length of next hop address" field. Hence, it is
      always clear whether the address is an IPv4 address (length is 12)
      or an IPv6 address (length is 24).  If the length of the next hop
      address is neither 12 nor 24, the MP_REACH_NLRI attribute MUST be
      considered to be "incorrect", and MUST be handled as specified in
      Section 7 of [BGP-MP].

Notes:

According to section 4.3.2 of RFC4364:
When a PE router distributes a VPN-IPv4 route via BGP, it uses its own address as
the "BGP next hop". This address is encoded as a VPN-IPv4 address with an RD of 0.
The MVPN should follow the same rule to use RD+IPv4 (len 12) or RD+IPv6 (len 24)
in "Network Address of Next Hop".
--VERIFIER NOTES--
as requested by the original poster:
https://mailarchive.ietf.org/arch/msg/bess/V3Qkf-Aeg3oIFiswDVRaSN43tyo/

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