SASL External Mechanism

[ms419@freezone.co.uk]

I've successfully installed and configured openLDAP with TLS support. I 
am trying to authenticate using the SASL EXTERNAL mechanism, as 
described in the Administrator's Guide. I can use TLS, but can't 
authenticate using EXTERNAL.

ldapsearch -x -H "ldaps://ldap" -s base -b "" supportedSASLMechanisms

supportedSASLMechanisms: GSSAPI

ldapsearch -Y EXTERNAL -H "ldaps://ldap" -s base -b "" 
supportedSASLMechanisms

ldap_sasl_interactive_bind_s: Unknown authentication method (86)
        additional info: SASL(-4): no mechanism available: No worthy 
mechs found

How do I make the EXTERNAL mechanism available?

Thanks,

Jack