Set a static IP

Set a static IP on the server machine

open /etc/network/interfaces

sudo nano /etc/network/interfaces

then edit your interface entry (likely eth0) to look something like (you need to know your network details):

auto eth0
iface eth0 inet static
        address 192.168.0.100
        netmask 255.255.255.0
        gateway 192.168.0.1

reload network configuration:

/etc/init.d/networking restart