Resolvido usando a consulta abaixo:
ldapsearch -h hostname -p port -b "" -s base -D "cn=somecn" "(objectclass=*)" vendorversion objectClass isGlobalCatalogReady vendorname
Resultado:
version: 1
dn:
vendorversion: Sun Java(TM) System Directory Server/5.2_Patch_4
objectClass: top
vendorname: Sun Microsystems, Inc