The dhcpd-0.70 that comes stock with RH 5.2 wraps the DHCPREQUEST as a bootp packet rather than a DCHP packet. This causes routers that are configured to relay DHCP but not BOOTP to drop the DHCPREQUEST. Consequently, RH 5.2 cannot get an address unless it is requesting from the same subnet as the DHCP server is on.
We've replaced dhcpcd with pump