Multicast on a 2K Fex
I just had an issue where I was attempting to do a packet capture on a 2K Fex that was attached to a Nexus 5K. Since you can’t use the Fex port as a destination I had the destination port on the 5K itself, while the source was on Fex 7. Once I started the capture I received a ton of multicast traffic that I wasn’t expecting. The server I was capturing should have had very little traffic and no multicast at all. It turns out that another port on the same Fex was doing pulling in multicast due to a cabling error. The multicast reciever was never supposed to be plugged into this network. The 127 Megs of video the multicast receiver was pulling in, was going to all the ports on that particular Fex. It was almost like turning off igmp snooping so the multicast traffic was flooding everywhere.
I then changed my source to a different server on a different Fex and I could not see the multicast. Which means that the multicast at least was only affecting the Fex that the receiver was plugged into which was good. The 5K also showed the multicast traffic in its igmp and mroute table as you would expect. Basically using multicast on a 2K fex is a bad idea for all of the other traffic on the Fex.