I manage to hang my linux box!
Yes, my Linux box hang, and this is what I've did:
boot up, and up the interface eth1, then I wanted to change it to eth0 instead and figured out that I could just change the mac address in the config file at /etc/sysconfig/network-scripts/ifcfg-ethX. So I went on and configure that and hoping to give it a reboot and get it switched.
Unfortunately, it hangs! and it won't response to Ctrl + Alt + Del as well, so even with a KVM over IP, it doesn't help. Eventually I have to get the Data Center technician to reset it for me.
It is a known issue though, you can here: