I read some docs(BRKDCT-3101) on CISCO live which talks about multicast replication.
Needed clarification on a few concepts:
1) There is an internal group id which is used and multiple (S,G) entries
share the same group id. Does each mroute map to an internal group?
N9K# bcm-shell mod 6 "ipmc table show"
SRC IP ADDRESS MC IP ADDRESS MC GROUP VID VRF COS HWIDX CLASS HIT
220.127.116.11 18.104.22.168 0x2000007 0 1 0 75680 1 no
0.0.0.0 22.214.171.124 0x2000007 0 1 0 86578 2 no
2) What is a replication group?
I am trying to connect the dots from control plane (mroute) to what happens
inside the ASIC. How does a mroute (Source IP, Group IP, OIF list) get mapped and replicated internally ?
you are looking at a detailed session about Nexus 9000.
I think slide 19 provides in a graphic way how a multicast packet is handled.
My guess a replication group is the list of modules and ports that should receive a multicast stream.
Remember that there is not a one to one corrispondence between an IPv4 multicast address and the corresponding MAC address: only the less significant 23 bits are mapped on the MAC address so 32 IPv4 multicast addresses share the same MAC address.
Hope to help
Thank you for the reply. I was actually looking for some additional details.
I found the picture in the attached file on the net.
It shows the various blocks, but doesn't elaborate on how a route entry in
MRIB gets mapped to a hardware entry in ASIC and how the replication
happens. There seems to be multiple steps involved in ASIC and that's
what i'm looking for.