I believe (maybe incorrectly) that CentOS uses dhclient.conf for dhcp configuration.
According to 'man dhclient.conf' "The configuration file can also be preinitialized with addresses to use on networks that don’t have DHCP servers.". Unfortunately, I can't seem to find dhclient.conf, maybe it's being renamed/redirected/? via init scripts, I don't know.
I'll keep looking, thanks though.
Edit: Interesting link
. Too bad it doesn't apply to 4.4