# Closing the IPv6 First-Packet Gap with GRAND

DevFeed: [Closing the IPv6 First-Packet Gap with GRAND](<https://devfeed.tech/articles/closing-the-ipv6-first-packet-gap-with-grand-11450.md>)

Original publisher: [Read original article](<https://labs.ripe.net/author/pouria/closing-the-ipv6-first-packet-gap-with-grand/>)

Author: Seyed Pouria Mousavizadeh Tehrani

Published: 2026-09-04T13:32:29Z

Content type: article

Language: en

Sources: [RIPE Labs](<https://devfeed.tech/sources/ripe-labs.md>)

Topics: [Network](<https://devfeed.tech/topics/network.md>), [Internet](<https://devfeed.tech/topics/internet.md>), [reactive](<https://devfeed.tech/topics/reactive.md>), [Latency](<https://devfeed.tech/topics/latency.md>)

Tags: [competition](<https://devfeed.tech/tags/competition.md>), [internet](<https://devfeed.tech/tags/internet.md>), [ipv6](<https://devfeed.tech/tags/ipv6.md>), [latency](<https://devfeed.tech/tags/latency.md>), [network](<https://devfeed.tech/tags/network.md>), [open-source](<https://devfeed.tech/tags/open-source.md>), [reactive](<https://devfeed.tech/tags/reactive.md>)

## AI overview

The article explains an IPv6 Neighbour Discovery asymmetry: a host can reach its router immediately after configuring an address, while the router may not yet know how to reach the host. This can delay or drop the first return packets. GRAND addresses the gap by having the host proactively advertise its address, and the article describes an implementation of this mechanism in FreeBSD.

## Source excerpt

There is a subtle asymmetry in IPv6 Neighbour Discovery: a host knows how to reach its router before the router necessarily knows how to reach the host. GRAND fixes that asymmetry by making the host proactively advertise its address, and I implemented that mechanism in FreeBSD.