Comment 1 for bug 1063923

The problem is that the value "external" isn't currently supported by the package configuration and it is incorrectly replaced by auto as a default value. Current supported values are: auto, LOGIN, PLAIN, NTLM, CRAM-MD5, DIGEST-MD5, GSSAPI, OTP.

The "EXTERNAL" value will be added as a possible value.

Btw, using debconf-set-selections and using dpkg-reconfigure is not a supported way to update the configuration because the current configuration is always read from the configuration file in order to preserve configuration changes outside debconf. The only situation where preseeding would work is on initial installation when the configuration file is absent.

The change in SVN is at:
  http://arthurdejong.org/viewvc/nss-pam-ldapd?revision=1778&view=revision