Sophos XG LDAP (Domain) Join

Sophos XG V1

I want to join Sophos Firewall to LDAP domain, I ahve Zentyal V5.0.8 as my primary Domain Controller.

 

While Joining Domain  I am confused in these fields, Please help me to join Sophos in my LDAP Domain.

I have little bit idea about Base DN rest I am confused where I can find.

 

Base DN*

Authentication Attribute*

Email Addr Attribute *

Group Name Attribute*

Expiry Date Attribute*