ipv6 neighbor cache question

[Mikal Sande]

Is the IPv6 neighbor cache supposed to not inlcude incomplete entries? When my freebsd box resolves a previously unknown ipv6 address with ndp it does not add anything to the neighbor cache before it gets a reachability confirmation. I have viewed the neighbor cache with ndp -a.

The ipv6 addresses in question are local, so I am pretty sure that on-link determination is not interfering. The same thing happens with both link-local and global addresses.

When I ping an unused ipv6 address I do not find any corresponding incomplete 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.

My box is currently running.
FreeBSD hostname 10.0-RELEASE FreeBSD 10.0-RELEASE #0 r260789: Thu Jan 16 22:34:59 UTC 2014     root at snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC  amd64

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Mikal Sande