I have seen large numbers of multicasts on one specific portion of my network. I cleared the counters and within a weeks time I saw upwards of 26 million multicasts on one switch that only had less than 15 users on it. I have noticed high multicast numbers on certain ports on switches while others have none. I know about using port storm control to keep the multicast traffic to a controllable level, but I have a few older switches that don't support the command, and I was hoping there was a way I could keep multicasts confined at least within the switch that is generating the multicast.
Also, I have noticed at least 40 printers in this building who's interfaces are showing 10Mb/s Half Duplex, and of course I am seeing a lot of collisions on the ports. Could this cause a latency problem if the collisions become excessive? I am assuming these printer NIC's can't do 100 Full Duplex, so would it be a good idea to change the switchports to match the settings they are getting from auto-negotiation? I believe the latency issues are the result of excessive multicasts, but with the large number of printers they have I am trying to eliminate these old NIC's and Jet Direct cards as the cause of the issue.