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RFC8950 for a V4LESS(-AS) World: Diving into the magic of IPv4-with-IPv6 Next-Hops#

nog.fi meeting 2026.06 digest Program Core pick 16–17 June 2026

Abstract Recording

Daniel Wagner (DE-CIX), Tobias Fiebig (TU Wien)

Play the recording: RFC8950 for a V4LESS(-AS) World: Diving into the magic of IPv4-with-IPv6 Next-Hops

  • Why: The most directly relevant fabric/interconnect talk on the program. Carrying IPv4 routes with IPv6 next-hops dissolves several standing design pains in both IXP peering LANs and large ECMP fabrics — exactly the DC/WAN interconnect territory this PM works in.
  • What: A working walkthrough of what IPv4-with-IPv6 next-hops (RFC 8950, which extends RFC 5549-style extended next-hop encoding to eBGP) enables: IXPs without IPv4 peering-LAN growth pain, seamless IPv4 routing at /32 granularity, IPv4-free transport links, a fully ARP-free infrastructure, and ECMP-enabled L3 underlays for 100G+ fabrics without LACP. Includes an open invitation to peer with V4LESS-AS (AS215250), their live RFC 8950 testbed at an internet exchange.
  • How: IPv4 NLRI is advertised over BGP sessions using IPv6 next-hops, so the entire L3 core — peering LANs, transport, fabric underlay — can be IPv6-only while still serving IPv4 destinations; with no IPv4 at L2/L3, ARP disappears and routed ECMP replaces LACP-bundled L2 links.
  • Where applicable: A standards-based technique, not vendor- or org-specific in principle. Constraints: every router on the path must support extended next-hop encoding, and the ARP-free/no-LACP benefits are easiest to realize in greenfield or single-administrator fabrics. The V4LESS-AS testbed (AS215250) is the concrete proof point.