[Samba] Samba4 Secondary DC as Backup DC (redundancy)

[Sketch]

On Tue, 23 Jun 2015, Rowland Penny wrote:

> On 23/06/15 18:58, Daniel Carrasco Marín wrote:
>>  Hi,
>>
>>  I've sucessfull created a secondary DC using the wiki manual (
>>  https://wiki.samba.org/index.php/Join_a_domain_as_a_DC), and is working
>>  perfectly, user and groups are synced on both and I can use any of them
>>  for
>>  login using clients like Owncloud, Prosody, python scripts...
>>
>>  Now my question is: ¿how I can use that secondary DC as backup when the
>>  main fails?.
>
> If it is by DHCP, then the dhcp server needs to push out both DCs as 
> nameservers, if static, then each client needs to be set to use both DCs as 
> nameservers.

His quetion is a bit vague, but I would also assume he is using LDAP for 
authentication on Owncloud, etc.  In that case, he also needs LDAP to fail 
over.  Generally, you can just point LDAP clients at "your.ADdomain.com" 
(whatever it is), which resolves to the IP addresses of all of your DCs. 
If they fail to connect, they will usually retry and get another address, 
and connect to a different DC.