[root@server1 ~]# rpm -q dhcp
dhcp-3.0.1-54.EL4
[root@server1 ~]# service dhcp start
dhcp: unrecognized service
[root@server1 ~]# service dhcpd start
dhcpd: unrecognized service

should be:  


[root@ftp ~]# service dhcpd stop
Shutting down dhcpd:                                       [  OK  ]
[root@ftp ~]# service dhcpd start
Starting dhcpd:                                            [  OK  ]
[root@ftp ~]#
[root@ftp ~]# rpm -qf /usr/sbin/dhcpd
dhcp-3.0.1-54.EL4
[root@ftp ~]#