Things to consider:
1.) I have a TAC open for over a month now with no real movement on resolving the issue.
2.) The description of the issue is short because I've spent countless hours looking into this and narrowing down the issue.
We are running into an issue with layer 2 multicast at one of our co-location facilities. We just installed these c9500 switches earlier this year. Essentially whenever a multicast video stream needs to be replicated to more than one egress port on either of our two c9500s, we get continuity count errors on the stream. These errors indicate either dropped or out of order packets which causes the video stream to break up. At most we can get several errors every few minutes. They come in groups of about 5 at a time. We don’t see the issue with unicast video or a multicast video stream with only one subscriber port on the LAN. Issue only occurs if multicast stream has to be replicated ot multiple ports.
Topology is primary router (mrouter) ASR 1k, Secondary router (querier) ASR 1k, primary and secondary switch are c9500s with port-channel between them. Most traffic including streams tested and verified dropping are coming in via the primary router.
The there are no corresponding interface errors or control-plane policy-map drops. "show controller cpu-interface" does have incrementing "SW Forwarding" drops, but this same category does not drop on the control-plane policy-map.
I'm convinced we are running into a limitation of multicast replication throughput or this is a weird unknown bug. the uplink to the primary router which has most the traffic on it has around 3 Gb UL and DL on it. 25 Gb SFP port with 10 Gb SFP.
CPU usage is low, around 10%. I already tried adjusting CoPP policy pps for various classes including SW Forwarding.
