[ofa-general] Re: OpenSM IPv6 consolidation

[Jason Gunthorpe]

On Thu, May 29, 2008 at 02:35:35PM -0700, Ira Weiny wrote:
 
> But that begs the question: Can a node issue an SNM request to a node in
> another IB subnet?  (I think the answer is yes if the IP subnet spans more than
> one IB subnet)  In that case, the SNM address would be in the range
> ff02::1:ff00:0/104 but what MGID would that map onto in IB?  I think the
> current mapping results in an IB link-local scope.  So would a router have to
> forward it even though the IB scope is link-local?

IP (v4 and v6) 'link local' traffic (ie IPv4 broadcasts and IPv6 link
local multicast) use MGID scope bits that are dependent on the
configuration of the IPoIB stack. Today linux and everyone else uses
link local MGID scope. There are patches floating about to make this
configurable like pkey so that you can have a global IB scope IPoIB
subnet. We used that patch set at SC07 to demonstrate IPoIB running
single subnet across IB routers.

Jason