The ``Default referral'' field prompts for the identifier of a host to be used, by default, for LDAP referrals from the current daemon. These allow LDAP databases to be combined.
The referral entry acts as a mount point, glueing two slapd databases together. A referral entry has an objectclass of ``referral'' and is named by a ref attribute containing a URL pointing to the slapd holding the data below the mount point. This mechanism is very general and allows slapd databases that are not normally hierarchical to be grafted together.
For example, suppose your company is running a slapd and just purchased a new company, also running a slapd. You can easily connect the two databases by creating an entry like the following in your slapd's database:
dn: ref="ldap://new.host/o=New Company,c=US", o=Your
company, c=US
objectclass: referral
ref: ldap://new.host/o=New Company,c=US
Now any subtree search that has this entry in its scope will return a
referral to the new company, in addition to any entries matched in your
database. Referral-aware clients will continue the search at the new
company's server.
A referral is issued when an incoming request lies outside the hierarchy for which the LDAP server contains entries. This hierarchy is specified with the ``Suffixes'' option on the LDAP server.
Enter a host name or IP address, with ``ldap://'' as a prefix, or else click on the Select a host button adjacent to the text field. Select from the list, which gives the known hosts on the sub-net. This host selection screen is described in ``Specifying a host''.