Nothing left to take away#

Remco van Mook

• Why: draft-ietf-intarea-ipv6-resolved-gateway removes ARP from access and hosting segments while keeping dual-stack hosts unmodified — a structural simplification aimed squarely at datacenter fabrics, containers, Kubernetes and GPU clusters running out of RFC1918.
• What: A mechanism that lets IPv4 service endpoint identifiers survive on an IPv6-only segment: hosts get a sentinel IPv4 gateway (DHCPv4 Option 3, placeholder 192.0.2.11) and resolve its MAC from the IPv6 neighbour cache instead of ARPing; unmodified hosts still ARP for the sentinel and the router answers — both host generations coexist on the same segment, with no DHCPv4 client/server/relay changes.
• How: Updated hosts use the RFC 4861 default-router list and RFC 4191 preferences (no ARP at all); gains include active/active gateways without FHRP, inbound ECMP to the last hop, no ARP spoofing, no broadcasts, per-host /32s anywhere in the footprint, and — via RFC 8950 — IPv4 service addresses delivered straight to pods without SNAT/DNAT/conntrack. Running code exists on the host side (v4gwd.py for ifupdown/NetworkManager, a systemd-networkd patch, FreeBSD 13.1+).
• Where applicable: Target use cases are explicitly DC fabrics, campuses, DOCSIS MAC domains, FTTH/PON aggregation, containers/Kubernetes, and AI/GPU clusters. Draft stage (-01 will add ND health prerequisites and a MAY-level ARP fallback), so it needs host-side adoption; the design is general.