static IP under F10

[Rafnews]

Hi,

i have setup a static IP for my F10 computer (which will be use later as DB
server for test development).
therefore i modify the following 3 files:
/etc/sysconfig/networking/devices/ifcfg-eth0
/etc/sysconfig/networking/profiles/default/ifcfg-eth0
/etc/sysconfig/network-scripts/ifcfg-eth0

i setup my mask to 255.255.255.0 as usual and after i reboot F10.
after login as user, F10 as setup eth0 inactive. when i press the button
activate, eth0 is activated but the mask turns to my default gateway
address... and internet does not work.

where is the problem ?
i'm sure that this IP address is free and works if i use it on windows OS.
thx a lot.