Date: Fri, 28 Mar 2014 09:20:12 -0700 From: =?ISO-2022-JP?B?GyRCP0BMQEMjOkgbKEI=?= <jinmei@wide.ad.jp> To: Mikal Sande <mikal@sande.im> Cc: FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: ipv6 neighbor cache question Message-ID: <CAJE_bqeHi-=AFP0ba82-1zqUJ%2Bqc62wJN87KGrZf_x=UHLnehQ@mail.gmail.com> In-Reply-To: <5334509B.8010706@sande.im> References: <5334509B.8010706@sande.im>
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At Thu, 27 Mar 2014 17:23:55 +0100, Mikal Sande <mikal@sande.im> wrote: > Is the IPv6 neighbor cache supposed to not inlcude incomplete entries? Wh= en my freebsd box resolves a previously unknown ipv6 address with ndp it do= es not add anything to the neighbor cache before it gets a reachability con= firmation. I have viewed the neighbor cache with ndp -a. > > The ipv6 addresses in question are local, so I am pretty sure that on-lin= k determination is not interfering. The same thing happens with both link-l= ocal and global addresses. > > When I ping an unused ipv6 address I do not find any corresponding incomp= lete entry in the neighbor cache afterwards. But, if I ping an unused ipv4 = address i do find an incomplete entry in the arp cache. I am curious as to = why this behavior occurs. Is it intentional? Is it by design? > > The reason for my curiosity is that I have not observed this behavior in = other OSes such as linux and openbsd. I suspect that's something specific to recent versions of FreeBSD. The very original kernel neighbor cache and ndp implementations of the KAME project should have behaved as you expected above and actually saw with OpenBSD. I don't know if the change was intentional or a kind of defect, though. Hopefully someone more familiar with recent updates in FreeBSD can clarify that. -- JINMEI, Tatuya
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