The CPU server will have to get it's kernel locally and if
there's no DHCP server, you need to tack the ip addresses
onto the bootargs line:

bootargs=il <ip addr> <ip mask> <net addr> <fs addr> <auth addr>

You'll also have to make the key/authid for the file sever and
the cpu server the same.  If a cpu server can't find an auth server
to answer, it just guesses that the key/authid for the fs are the
same as its own and handcrafts a ticket to use.  That's the
chicken and egg problem.

Of course, if somewhere else you have a dhcp server, you can get
the kernel off the net too.