https://www.cisco.com/c/en/us/td/docs/security/esa/esa120/user_guide/b_ESA_Admin_Guide_12_0/b_ESA_Admin_Guide_chapter_01100.html

The following are the prerequisites to integrate Active Directory with Cisco ISE.
+ Use the Network Time Protocol (NTP) server settings to synchronize the time between the Cisco ISE server and Active Directory. You can configure NTP settings from Cisco ISE CLI.
+ If your Active Directory structure has multidomain forest or is divided into multiple forests, ensure that trust relationships exist between the domain to which Cisco ISE is connected and the other domains that have user and machine information to which you need access. For more information on establishing trust relationships, refer to Microsoft Active Directory documentation.
+ You must have at least one global catalog server operational and accessible by Cisco ISE, in the domain to which you are joining Cisco ISE.
The following are the prerequisites to integrate Active Directory with Cisco ISE.
+ Use the Network Time Protocol (NTP) server settings to synchronize the time between the Cisco ISE server and Active Directory. You can configure NTP settings from Cisco ISE CLI.
+ If your Active Directory structure has multidomain forest or is divided into multiple forests, ensure that trust relationships exist between the domain to which Cisco ISE is connected and the other domains that have user and machine information to which you need access. For more information on establishing trust relationships, refer to Microsoft Active Directory documentation.
+ You must have at least one global catalog server operational and accessible by Cisco ISE, in the domain to which you are joining Cisco ISE.
Reference:
b_ISE_AD_integration_2x.html#reference_8DC463597A644A5C9CF5D582B77BB24F The following are the prerequisites to integrate Active Directory with Cisco ISE.
+ Use the Network Time Protocol (NTP) server settings to synchronize the time between the Cisco ISE server and Active Directory. You can configure NTP settings from Cisco ISE CLI.
+ If your Active Directory structure has multidomain forest or is divided into multiple forests, ensure that trust relationships exist between the domain to which Cisco ISE is connected and the other domains that have user and machine information to which you need access. For more information on establishing trust relationships, refer to Microsoft Active Directory documentation.
+ You must have at least one global catalog server operational and accessible by Cisco ISE, in the domain to which you are joining Cisco ISE.
b_ISE_AD_integration_2x.html#reference_8DC463597A644A5C9CF5D582B77BB24F

A certificate signing request (CSR) is one of the first steps towards getting your own SSL Certificate. Generated on the same server you plan to install the certificate on, the CSR contains information (e.g. common name, organization, country) that the Certificate Authority (CA) will use to create your certificate. It also contains the public key that will be included in your certificate and is signed with the corresponding private key