On the DHCP server, verify that the tftp-server package is installed with the command rpm -q tftp-server. If it is not installed, install it via Red Hat Network or the Red Hat Enterprise Linux CD-ROMs.
For more information on installing RPM packages, refer to the Package Management Section of the Red Hat Enterprise Linux Deployment Guide.
tftp is an xinetd-based service; start it with the following commands:
/sbin/chkconfig --level 345 xinetd on /sbin/chkconfig --level 345 tftp on
These commands configure the tftp and xinetd services to immediately turn on and also configure them to start at boot time in runlevels 3, 4, and 5.