Technet article:

” Explanation:

When a requested object exists in the directory but is not present on the contacted domain controller, name resolution depends on that domain controller’s knowledge of how the directory is partitioned. In a partitioned directory, by definition, the entire directory is not always available on any one domain controller.

An LDAP referral is a domain controller’s way of indicating to a client application that it does not have a copy of a requested object (or, more precisely, that it does not hold the section of the directory tree where that object would be, if in fact it exists) and giving the client a location that is more likely to hold the object, which the client uses as the basis for a DNS search for a domain controller. Ideally, referrals always reference a domain controller that indeed holds the object. However, it is possible for the referred-to domain controller to generate yet another referral, although it usually does not take long to discover that the object does not exist and to inform the client. Active Directory returns referrals in accordance with RFC 2251. ”

Atlassian KB article: