The file /etc/sysconfig/network is a global (across all network cards) configuration file. It tells the system boot scripts whether we even want networking.
It can contain things like:
NETWORKING=yesHOSTNAME=myboxGATEWAY=192.168.1.1The absence of this file signals the system boot scripts to not even bother going through the /etc/sysconfig/network-scripts/*, which is why your /etc/sysconfig/network-scripts/ifcfg-eth0 file was never even used before you touched the /etc/sysconfig/network file.
