Comment 7 for bug 1524452

So unless ifup/ifdown brings the aliases up/down itself, I don't think filtering those out is the right fix.
Take this scenario as an example:
 - System boots quickly
 - networking.conf kicks in, fails to bring eth0 because it's not showed up yet (happen reasonably often with complex blade systems)
 - network-wait kicks in
 - eth0 does show up
 - interface is brought up but not the eth0:X ones

The interface labeling thing isn't as cool as it used to be and most people just add multiple IPs on the same interface nowadays, it used to be that ifconfig and other tools were confused by that, but they're not anymore.

Anyway, I guess people are still using that feature and so it's probably worth fixing. The fix I'd suggest is to do something similar to the bridge-utils and vlan udev hooks, that is, have a udev hook which triggers on new interfaces, have the hook use ifquery to check for downstream interfaces (INTERFACE:X) and then bring those up.