i've experienced this same problem. what appears to be working for me is maintaining name resolution control with the local HOSTS file rather than our DNS services.
this file can get large after hundreds of nodes, luckily they don't change static IP addresses too often. good luck.
Thanks very much for that - I've done the same , but on occasions some seem to slip the net , and I wonder if it's due to a cacheing issue within Orion . do you need to do anything to retain "visibilty " of the HOSTS file in any way by for example a batch job such that any cache is maintained ?