Ubuntu Server 12.04 still changes ip address after setting static ip in /etc/network/preferences
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I recently set up an ubuntu 12.04 box to help me do some web crawling. The box is on the same network as my computer, but frequently changes it's ip address so I can't ssh into it. 


After following some instructions to set up a static ip on my machine, my /etc/network/interfaces file currently reads:

    auto lo
    iface lo inet loopback

    auto eth0
    iface eth0 inet static
    address 192.168.50.64
    netmask 255.255.255.0
    gateway 192.168.50.1

I've found that if I restart the box, the ip address is always 192.168.50.64, but eventually changes to something else like 192.168.50.23.

Am I missing a step in configuring a static ip? 

 