Just wanted to mention that we have reported the exact same problem to
Novell in March. (NetWare 6 SP4 - 2 node clusters) and the call is still
open. Its now been escalated to their connectivity team.

Changed subnet mask and now cluster nodes not able to join. Master nodes
doesn't send out any heartbeat packets.

We have two NetWare 6 clusters located in two different locations and
after changing the subnet mask on both from to
the cluster will not join. If we change the subnet back to its old setting
its fine again.

Now that we have read this thread we have informed Novell of it and we're
awaiting their response, as we would be very interested to see if this is
recognised as a bug and that they are working on a fix.