I have a simple flat network with about 20 - 3Com 4200 series switches in it. The 3Coms have IGMP snooping enabled to forward multicasts correctly and STP Fast Start is enabled as well. Broadcast storm control is disabled and flow control is disabled too. On smaller networks at other locations that also use these 3Com switches I have no problems with Multicast sessions finishing. However, in this bigger network I will get random machines dropping out of the multicast session. They will image fine in a unicast session. For some reason they do not want to play nice in a multicast. The core switch is a dell 6248 and the Dell has multicast forwarding enabled as well as broadcast storm control disabled. Has anyone else had this type of issue multicasting with 3Com 4200 series switches? I'm running firmware version 3.0.4 on all the 3Com switches. I've gone through the forums and haven't had any luck so far finding something that matches our situation.

Any help would be appreciated,

William Sixsmith