During reboot,the dhcpd daemon regularly but intermittently fails to start. A
view of the service status shows that it was unable to contact the LDAP server.
Once the LDAP server has started, starting manually works.

Looking at /usr/lib/systemd/system/dhcpd.service (and dhcpd5.service) there is
an entry of 

After=remote-fs.target network.target nss-lookup.target time-sync.target
ldap.service ndsd.service

There appears to be no ldap.service. A look at systemd-analyze plot shows the
dhcp services starting before slapd and slapd taking about a minute to start.

The only service that provides LDAP is slapd.service.

ldap.service is referred to in dhcpd.service dhcpd6.service dhcrelay.service
dhcrelay6.service and postfix.service