[Samba] AD domain failover not working

[Sankar T Natarajan]

Hi,

I have AD domain controllers running samba 4.2 turnkey linux (domain
controller).

Well I am trying to evaluate the failover while Primary AD is down and
backup take position and serve to the client's request.

dc1.linuxad.org
dc2.inuxad.org

If my Primary AD(dc1) is down, my "Active Directory Users and Computers"
management console failed to retrieve objects. I couldn't see any of the DC
in the list.error is https://i.stack.imgur.com/uKdhz.png

I couldn't change the password through windows while the DC is down. my DNS
address is pointed to dc2 IP address, but still error.
https://i.stack.imgur.com/aXogj.png

These are my steps I have done,

1. Transferred the Infrastructure Master role to dc2 for replication take
place in time.
2. according to Microsoft AD, Infrastructure Master role should not
accompany with GC server, the dc2 is became GC while enrolling as domain
controller.

my queries are:

1. the above two points are actually exemplify the Microsoft AD term in
this Samba AD services?

2. what is the purpose of backup AD here, which is not serving while
primary is down?

Are these issues because of the samba version which I am using ?