The only publicly visible/accessible Unix server in the computer science department is k200.ecs.csun.edu. In order to access the other Unix machines in the department, you should use k200.ecs.csun.edu as a gateway (meaning that you need to first SSH into k200, and then from that machine, ssh into any of the available Unix machines). Another possibility is to first VPN into CSUN first before attempting to connect to any of the Unix machines.
In the following webpage you can find instruction on how to use VPN:
http://www.csun.edu/it/vpn