On Fri, 2009-07-24 at 01:57 -0700, Jesper Dangaard Brouer wrote:
quoted text
> On Thu, 23 Jul 2009, Jeff Kirsher wrote:
> 
> > From: Alexander Duyck <alexander.h.duyck@intel.com>
> >
> > This patch moves all of the multicast addresses out of the free Receive
> > address registers and instead programs them all into the multicast table
> > array.  As a result the multicast filtering may not be as precise, but it
> > also greatly reduces the overhead for multicast addresses.
> 
> What do you mean by "the multicast filtering may not be as precise" ?
> 
> I'm planning to use these NICs for multicast traffic (both routing and 
> monitoring).  Is there any precausing I need to be aware of?
> 

The receive address registers, or RARs, are perfect match filters.  The
multicast table array, or MTA, contains hashed values of the multicast
addresses.  Therefore, it isn't a perfect match for the multicast
addresses anymore.  But to support a larger number of multicast
addresses, they can't be written to the RARs, since those resources are
small and are needed for MAC and unicast address filtering.

Cheers,
-PJ Waskiewicz

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