GoKawiilFreeBSD gets GRAND implementation to fix IPv6 first-packet delay
A FreeBSD contributor has implemented GRAND (Gratuitous Neighbour Advertisement), a mechanism that addresses an asymmetry in IPv6 Neighbour Discovery where a host can reach its router immediately but the router may not yet know how to reach the host. Under GRAND, the host proactively announces its new IPv6 address so the router already holds a Neighbour Cache entry before any return traffic arrives.
GoKawiil's interpretation of the reporting above, not reported fact.
Without this fix, the very first return packet of a new connection can be delayed or dropped while the router performs address resolution, hurting perceived network responsiveness right when a device joins a network. Baking GRAND into FreeBSD's networking stack removes a longstanding latency source in IPv6 address configuration without requiring changes on the router or remote host side.
- IPv6 Neighbour Discovery has an inherent asymmetry: hosts can reach routers before routers can reach hosts.
- GRAND has the host send a gratuitous advertisement so routers pre-populate their Neighbour Cache.
- The FreeBSD implementation aims to eliminate first-packet latency or drops during IPv6 address setup.
Source: labs.ripe.net, 2026-09-15
Published there as: “Closing the IPv6 First-Packet Gap with Grand”
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