Hello,

Here is my scenario. Clients A and B can succesfully be cloned from a server running udp-sender when connected together via a hub. Either one can also be successfully cloned as the only client to the server when connected on the switch (as I understand it, this scenario is actually unicast, not multicast). When attemping to clone clients A and B on the switch simultaneously, Client A writes:

---------- udpreceiver for /dev/hda2 at 10.90.0.172 on eth0 received message cap=00000019 connected as #0 to 10.90.0.167 listening to multicast on 234.90.0.167 ---------- and then writes nothing else. Client B is similar.

The server writes numerous lines like this: ------------- Timeout notAnswered=[1] notReady[1] nrAns=0 nrRead=0 nrPart=1 avg=65625 -------------

After what seems like a couple of minutes, the clients drop off and then the server stops.

We are using a class B subnet which initially gave me problems, but after specifying the broadcast address on the DHCP server I can confirm the clients and server are all using a bcast address of 10.90.255.255

We are using a 3Com 4226T switch and in the list archives I see several references to problems with 3Com switches and IGMP. I have disabled IGMP querying and snooping, and disabled broadcast storm control. Flow control can be specified per port - so for the 3 ports that these machines are connected to, I've disabled flow control, disabled auto-negotiate, and set to 100Mbps full duplex. (There are other active ports in use on the switch and I've left those on auto-negotiate with flow control.)

Does anyone have some advice?

Thanks for your time, Andrew Cameron Systems Administrator Vermont Legal Aid, Inc.