Re: IPv6 - NS, DAD and MLDv2 interaction

On Wed, Feb 23, 2022 at 01:46:32PM +0000, Scheffenegger, Richard wrote:
> As far as I know, an IPv6 host initially tries to perform Duplicate
> Address Detection, as well as Neighbor Discovery / Neighbor Solicitation.
> All of this typically works on Ethernet, by mapping into a well-known
> Ethernet multicast destination MAC “33-33-xx-xx-xx-xx”.

Yup. IPv6 replaced broadcast by multicast on the link layer.

> It appears that some vendors of switches have started to become overly
> restrictive in forwarding Ethernet Multicast, and only deliver these *after*
> a Host has registered itself to receive / participate in specific IPv6
> Multicast groups.

May you please drop an information about the vendor?
So that we can warn the community to buy those broken products.

> So far, I could not find any guidance (and with my lack of depth into
> IPv6, it is also unclear to me, if this would even be possible) if
> registering a host into a IPv6 MC group via MLDv2 in order for it to receive
> NS, ND, DAD is something that would be expected…

https://datatracker.ietf.org/doc/html/rfc4861#section-7.2.1

The host must join (using MLDv2) the multicast groups for all of its own
addresses to be reachable by Neighbor Discovery. This does not include the
standard RD group (IIRC).