I have installed SuSE9 AMD64 on a dual Opteron system: http://www.appro.com/product/server_1122h_2.asp I had no problems at all with installation and everything is running as I would expect with one exception: I am unable to recieve multicast datagrams sent from another machine on our network. I am able to send and receive from two programs on the same machine. I am able to send from AMD64 to another machine, but I am unable to receive datagrams sent from any other machine. (BTW, one of the other machines is the same hardware running SuSE 9 32bit). I upgraded from the tg3 network module to the bcm5700 module downloaded from broadcom with no effect. I upgraded to the k_smp-2.4.21-143 from ftp://ftp.suse.com/pub/people/aj/Kernel-AMD64 with no effect. I'm able to reproduce the problem with my own code as well as a couple of very simple java programs I found here: http://www.linuxsocket.org/books/Sockets/programs/ Grab SimpleMulticastDestination.java and SimpleMulticastSource.java. These programs use the MC group 224.0.0.1 which works, but others (236.0.0.1 for instance) do not. Has anyone else noticed this behavior or heard of multicast or IGMP problems on this platform? Kelly Burkhart