Authentication with different port and users

Hi, I used to have freeradius(old version) installed on Solaris and have 2 separate processes listening on port 1812 and 1645. They authenticate 2 groups of different users. I upgraded and installed freeradius 2.1.11 on CentOS 5.6. According to radiusd.conf, I could get freeradius listen on different ports. Can I config the ports authenticate different groups of users using "/etc/passwd"? Thank you. Regards Alan