[openib-general] question regarding GRH flag in ib_ah_attr

[Hal Rosenstock]

On Wed, 2006-05-10 at 21:26, Hal Rosenstock wrote:
> On Wed, 2006-05-10 at 19:44, Roland Dreier wrote:
> >     Sean> Does anyone know how the user determines if the grh flag
> >     Sean> should be set in the ib_ah_attr when allocating an ib_ah?
> >     Sean> Do they do this by examining the GIDs in a path record?
> > 
> > Good question.  It's always needed for multicast, of course.  For
> > unicast, I guess one could look at whether the subnet prefixes of the
> > SGID and DGID are the same, but I'm not sure that's sufficient -- a
> > router could conceivably sit between two subnets with the same subnet
> > prefix.
> 
> Huh ? In this case, aren't the subnet prefixes are required to be
> different ?

Not just different but globally unique, right ? 

What you are describing is similar to a NAT function for IB which would
need to be supported in the IB edge router to that private network.

-- Hal

> 
> -- Hal
> 
> > Perhaps some of the Obsidian guys could comment?
> > 
> >  - R.
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