cluster configuration: gigabits switch connection to an external machine

I have a linux cluster on CenOS, with a gigabit switch bridging all
the nodes, and want to mount an external linux computer's file system
onto the cluster machine's file system. I have plugged in an Ethernet
cable from the external linux box (Ethernet card out) into one of the
free jackets on the gigabit switch.

Now my question is, how may I configure the cluster machine in order
to achive that?
(I am a newbie so please show certain details or point me to a
resource for details would be appreciated)

Thanks in advance!

Joe