FYI, this has been resolved by adding ObjectClass"domain" to the
"dc=xxxx,dc=xx"
# ldapsearch -h ca-ldap01 -b "dc=redhats,dc=rs" -s sub
"objectclass=nisdomainobject"
version: 1
dn: dc=redhats,dc=rs
nisDomain: redhats.rs
objectClass: top
objectClass: domain
objectClass: nisdomainobject
dc: redhats