[CentOS] Weird behaviour of ifcfg scripts

Hi,

I accidentally found that the existence of a file e.g. named 
ifcfg-eth1:1 put in /etc/sysconfig/network-scripts/ leads to the 
appropriate interface being created even with the option 'ONBOOT' set to 
'no':

DEVICE="eth1:1"
BOOTPROTO="static"
NM_CONTROLLED="no"
ONBOOT="no"
TYPE="Ethernet"
IPADDR=12.34.56.78
NETMASK=255.255.255.0

Is that intended behaviour?