Overview
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In CUCM, there are several primary user journeys for directory search:

* Cisco Jabber (soft clients)
* Corporate Directory IP Phone Service (physical phones)
* 3rd-Party Integrations, such as:

  * CUAC
  * Billing

* In CUCM 10.6 and 11.0, Jabber (when integrated using UDS) requires all users
  provisioned in all clusters, which is problematic as it introduces userid
  duplication during data syncs.
* The CUCM 11.5(1) LDAP Search feature supports seamless support multi-cluster
  directory search. This means the external directory is used with UCM acting as
  a UDS Proxy for directory Search requests.

  * LDAP Search may be mandated for customers deploying MRA (Mobile and Remote Access),
    as this is a required configuration to support directory search outside the
    Enterprise for several directory integrations.