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

eth0 - IP:

eth0:5 - IP:

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?

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Does ONPARENT=yes declaration exist in your alias configuration file? That directive will bring "up" the alias when the parent is brought "up".

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up vote 0 down vote accepted

I resolved the problem by disabling NetworkManager service. Probably, if you need that service to be active, you can take in account the Tim's suggestion, or you can make use of NM_CONTROLLED=no option. Anyway, with this option used, I think you will need to do some other settings.

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