This entry is really a paper that I have maintained on another wiki. However, that Wiki is disappearing so I have copied and updated that paper.
The paper discribes how to configure WebSphere Portal 7 or 8 security to use an attribute other than the Portal default to login.
For example, in IBM we have an enterprise LDAP known as Bluepages. On of the attributes in Bluepages is our external e-mail ID. This e-mail ID is also known as our intranet ID inside IBM. Most all the sites and applications we log onto inside IBM require the use of our intranet ID. However, this is NOT the Portal default.
By default, Portal uses the first element of your LDAP Distinguished Name (DN) as your login ID. This first element is known as the Relative Distinguished Name (RDN). Many times, like inside IBM, Portal needs to be configured to use an attritbute in the LDAP record as the login ID.
This paper describes the process for WebSphere Portal to use an attribute other than the RDN (of the DN) for login.
The paper is attached here.