[openib-general] IPv6oIB neighbour discover broken when MCGs overflow

[Shirley Ma]

Roland Dreier <rdreier at cisco.com> wrote on 02/16/2007 09:25:30 AM:

>  > Even SM supports 1000 MCGs, it's still not sufficitent for 250 nodes
>  > cluster, each node have 4 links for IPv6 without any scope/global IPv6
>  > address configured.(250*4+ a few default MCGs) There will be a MCG
overflow
>  > problem anyway in IPv6oIB.
>
> But what's the problem with supporting 1000 or even 10000 MCGs?
>
>  - R.

I am not sure whether I understand your question. I am trying to answer it,
please let me know whether I am wrong.

Each IPv6 Link local address will create a unique solicited-node multicast
address, which will create unique full member of IB MCG, each other IPv6
address will create a solicited-node multicast address, whether it's unique
or not based on the groupID. So when IPv6 module being loaded in the
kernel, (or might be a part of kernel in the future) in SM, we will see
more than 1000 MCGs when IPoIB link up. Some of them can't join any MCGs.
Then IPv6 ND is broken with some of the nodes join failure.


Shirley Ma
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