Some IBM SP2 systems will already have a .rhosts file set up for you when you receive your account. However, on other systems, you may have to set up your own .rhosts file. This file should include the names of all the nodes and switches you may ever want to use.
Make sure that the node you are logged onto is in your .rhosts file. If it is not, you will want to add that node into the .rhosts file to avoid problems.