[c-nsp] Fun problem affecting only even-numbered ports

[John Neiberger]

This is a good one. I'm working with TAC on it, but I thought i'd
share it here, too, just because it's so unusual. We're seeing
intermittent drops on a multicast video stream and we haven't been
able to determine why. This is the second time we've seen this bizarre
behavior. At the urging of the TAC engineer, we tried moving receivers
to different ports and noticed that we only see the drops when the
receiver is connected to even-numbered interfaces! Odd-numbered
interfaces are not affected.

This is on a 7600 with SUP 720-3BXL and a 6748 linecard. What part of
the 6748 linecard architecture is responsible for a behavior
difference between odd- and even-numbered ports? This is a WS-6748-SFP
with a DFC-3BXL.

Any thoughts?