that's why 'ip addr add w.x.y.z dev eth0' is preferable--it doesn't delude you into thinking you have multiple interfaces, because you don't. try and add a rule for eth0:0 and let us know how it goes.
Other scripts that try to handle aliases match on both interface and IP; as you hinted, there's no way to handle aliases directly.
What's the standard way to store these settings so they take effect upon boot? Since /etc/init.d usually only contains scripts and not custom configurations, i guess /etc/sysconfig/network-scripts/ifup.d would be the one way of doing it.
Would something as simple as
#!/bin/sh
ip addr add 1.2.3.4 dev eth0
placed into that ifup.d directory work, or is there a better way of doing it? (Sorry for getting a little off topic here.) Thanks!
--Curby