I have on my `eth0` NIC card the following IP alias (I'm running CentOS 6.2):

`eth0` - IP: 192.168.50.1

`eth0:5` - IP: 10.0.0.1

Now, when I boot the server, both interfaces come up and respond, but if I try to run: `ifup eth0` or `ifup eth0:5`, it no longer permits me to keep them both up. Only the interface declared in the command will be up. The other will be disconnected.

Can anybody explain me why that happens, and how to bring up both interfaces when I need to reset one of them?