Code:
Mar 18 16:25:39 zmldap2 slapd[24934]: do_syncrep2: rid 100got search entry without control
Mar 18 16:25:39 zmldap2 slapd[24934]: do_syncrepl: rid 100 retrying
This would generally indicate that the server it is pointing at is not configured as a master, since it is not exposing the control necessary for replication.