[...]
http://www.centos.org/docs/5/html/Installation_Guide-en-US/s1-kickstart2-sta...
I'm not sure if this is totally what you're looking for but I hope it helps.
This pageĀ http://wiki.centos.org/TipsAndTricks/KickStart should be helpful as well. In theĀ Use a specific network interface for kickstart, quoted "A second method is using ksdevice=link. In this case anaconda will use the first interface it finds that has a active link." so you may wish to try that too.
HTH
-- Zack
cobbler@lists.fedorahosted.org