[c-nsp] Multicast replication over GRE on 7600s

[John Neiberger]

I have an architectural question. As an example, let's say you have
two 7600s directly connected via routed links running PIM and you have
primarily multicast traffic. If you're running egress replication
mode, you either have a Janus ASIC or Metropolis ASIC responsible for
the multicast replication, which happens on the line card. But how
would things change if you were not running multicast directly on the
routed link, but instead used a GRE tunnel between the two routers?

I guess I have a couple of questions:

1. How is GRE traffic processed in this scenario? Can it be forwarded
at high rates on the line card or is it punted to the CPU?

2. Which hardware is responsible for multicast replication over GRE tunnels?

Any ideas?


Thanks!
John