If you're on an SGI the usually needs the network to boot, and the
network is down, do the following to boot the machine network-less:

1. hit the reset button or power-cycle
2. hit ESCAPE to enter maintenance mode
3. select "Enter Command Monitor"
4. type "single"
5. supply the root password
6. hit ^D to go into single-user mode
7. use the chkconfig command to see what IRIX pieces are ON and OFF
 Turn off networking (see /etc/init.d/network script for details)
8. chkconfig nfs off
9. chkconfig yp off
10. chkconfig ntp off
12. chkconfig named off
13. chkconfig network off
13. chkconfig timed off
14. logout
15. select run-state 3

Reverse the chkconfig settings when the network is once again
available.  Note: with the network stuff shut off, selecting
"System->Shutdown" will take 45 seconds or so to respond.  Be patient.