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:
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LDAP: error code 12 - Unavailable Critical Extension
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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.
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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.