VPN with Authentication Active Directory with enumeration blocked

Question

Hi. 
 
 Anyone has configured Sophos XGS SSLVPN with Active Directory Authentication on AD with enumeration blocked? 
 After configure Server on XGS I can authenticate and retrieve groups/users without problem... My problem appears when try to authenticate user on VPN Portal/User Portal/SSL VPN... By the logs I can see a failure on search with filter sAMAccouname=xxxxxxx and result on user not found. 
 This is caused by blocked user enumeration on AD. 
 
 Is there any way to configure a Sophos to authenticate on AD with this configuration?

Hardik_R · Answer

Hello Tecnologias Imaginadas As per the authentication behavior on Sophos firewall, everytime when user logs in through any mechanism(VPN Portal/User Portal/SSL VPN) , firewall send that request directly to configured AD server using the "ADS user name" Now at AD server, the "ADS user name" will search the "user" within all domain users to identify user attributes(such as group membership etc) so I assume that when you block user enumeration on AD, the "ADS user name" is not able to search the user and hence you are getting "user not found" message. so, it seems to be necessary to allow enumeration for at least the user that you are using in " ADS user name" and for rest of the group/OU you can deny the read permissions(user enumeration). Considering the above behavior, I have some queries on your below 2 statement, what's the difference between them, who is able to authenticate and who is not able to authenticate? 
 "After configure Server on XGS I can authenticate and retrieve groups/users without problem... My problem appears when try to authenticate user on VPN Portal/User Portal/SSL VPN ..."