[c-nsp] Multicast Issue

[Tim Stevenson]

The similarity here has to do with the concept of destination indexes 
in 6500, but these two problems have 2 separate causes at a higher level.

The CSCds22021 has to do with flood traffic where the tx source port 
is also a member of the floodset (the flood index for the particular 
packet) for received packets. Source filtering prevents the flood 
packet from going out the original port, but doesn't prevent it from 
ending up on the SPAN dest port, which has the same indexes 
programmed as the SPAN source.

On the other hand, the PIM problem has to do with the destination 
index that PIM packets are sent to when snooping is enabled, which is 
basically a flood to all ports. Agree this is indeed suboptimal.

In any case, PIM is immaterial to this problem since there is only 
one router in the picture, so I would not discount the usefulness of SPAN.

Also, even for the PIM problem, you could always configure the SPAN 
dest port as a 1Q trunk & then you'd at least be able to figure out 
which PIM packets came from the vlan you are interested in.

Tim

At 08:55 AM 4/27/2006, Jay Ford pronounced:
>On Thu, 27 Apr 2006, Hank Nussbacher wrote:
> > Is this CSCds22021 you are talking about?   -Hank
>
>No, but it's related in that it seems to have the same root cause.  The
>situation we saw was not just traffic in the opposite direction of that
>intended, but PIM traffic from other ports showing up.  For example, I do a
>monitor of port te1/1.  Not only do I get traffic on te1/1, but I also get
>PIM on te1/2, te1/3....  Obviously, this behavior was very unhelpful.
>
>Jay
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Tim Stevenson, tstevens at cisco.com
Routing & Switching CCIE #5561
Technical Marketing Engineer, Catalyst 6500
Cisco Systems, http://www.cisco.com
IP Phone: 408-526-6759
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