When using the LDAP monitor to monitor a Sun Directory Server, if all the fields are set (i.e. base, bind, attribute), the following error may occur:
LDAP: error code 12 - Unavailable Critical Extension
This is caused by certain versions of the Sun Directory Server (v5 and pre-6.3) not supporting the PagedResultsControl extension that is required by the LDAP monitor.
You can avoid this issue by leaving the attribute field blank. This will allow the monitor to login to LDAP to see if the object specified in the bind exists.