Here is how I was able to configure static ip address on ubuntu server 10.04 on my vSphere center at my house:
sudo nano /etc/network/interfaces
change this:
auto eth0 iface eth0 inet dhcp
to this:
auto eth0
iface eth0 inet static
address 192.168.1.100
netmask 255.255.255.0
network 192.168.1.0
broadcast 192.168.1.255
gateway 192.168.1.1
Lastly, run this command to uninstall the dhcp-client
sudo apt-get remove dhcp-client
Now your server runs on 192.168.1.100 so go to your router (if you are running this at home like me) and change your port forwarding ports to 192.168.1.100.