We have an application that runs fine on an IBM RS/6000 H50 machine, all multicast message are sent and received ok). We run the exact same binaries on a H70 machine and the multicast is unreliable (ie, we consistantly lose 1% of messages) <br><br>AIX 4.3.2 <br>The filesets are the same on both machines (except for H70 64bit libs) <br>Ethernet adapter settings are the same (exact same ethernet cards in both machines.) <br><br> Any ideas? <br><br> Simon