Which Red Hat are you using ?
You say you're using RHEL3... Which update ? Also, are you using the 64bit version ?
I'm kickstarting Sun Fire V65x's over the network, and I had a problem with network devices. Under Red Hat, the machines believe that the top Ethernet connection is eth0. Under SuSE, they believe that the bottom Ethernet connection is eth0.
Under SuSE, the card chosen as eth0 matches the markings on the server. Under Red Hat, it seems to swap eth0 and eth1 according to the markings on the server.