NIS on SGI/IRIX

IRIX (AFAIK) has no direct support (I mean a GUI tool) to manage the use of NIS for passwd and groups - you can just turn NIS client on and configure the host resolution order.
So take care that nsswitch.conf is set up correctly (usually, it is!) and the /etc/passwd and /etc/group contains +::::: (or +:::) in the last line (or something similar ;-))
Otherwise you will have the problem that ypcat passwd delivers the expected useres, but non of these users can log in (Unknown user id).