[Samba] Authentication to Secondary Domain Controller initially fails when PDC is offline

James lingpanda101 at gmail.com
Fri Nov 27 15:00:37 UTC 2015

On 11/27/2015 9:49 AM, Rowland Penny wrote:
> On 27/11/15 14:30, James wrote:
>> On 11/27/2015 9:16 AM, Rowland Penny wrote:
>>> On 27/11/15 13:23, James wrote:
>>>> On 11/26/2015 11:12 AM, Ole Traupe wrote:
>>>>>>> Then you re-run your test with only DC2 up and running.
>>>>>>> Note DNS have need time to be updated if you are using others 
>>>>>>> DNS servers between clients and AD DCs.
>>>>>> The SOA RR identifies a primary DNS name server for the zone as 
>>>>>> the best source of information for the data within that zone and 
>>>>>> as a entity processing the updates for the zone.
>>>>>> The NS resource record is used to notate which DNS servers are 
>>>>>> designated as authoritative for the zone. Listing a server in the 
>>>>>> NS RR, it becomes known to others as an authoritative server for 
>>>>>> the zone. This means that any server specified in the NS RR is to 
>>>>>> be considered an authoritative source by others, and is able to 
>>>>>> answer with certainty any queries made for names included in the 
>>>>>> zone.
>>>>>> Much of the above was taken almost verbatim from online Microsoft 
>>>>>> tech documents.  I don't believe that DC's create NS records by 
>>>>>> default.
>>>>> You mean Samba DCs or DCs in general?
>>>>> I am not sure I understand the above. Do you suggest to create 
>>>>> another NS record for the Second_DC, or not to?
>>>>> In the resolv.conf on my member servers both DCs are listed as DNS 
>>>>> servers. I like to think that the member servers eventually ask 
>>>>> the second DNS server, if the first won't respond. This seems to 
>>>>> be reflected by ping taking more than 5 s for the first packet to 
>>>>> arrive.
>>>>> BUT what does the second DNS server (Second_DC) reply? Which logon 
>>>>> server does it announce?
>>>> DNS can be very confusing. You do not need to create a NS record 
>>>> for your second DC if the zone is directory integrated. By default 
>>>> the DC is authoritative for that zone.
>>> Probably with windows it is, but not with Samba AD, you only get one 
>>> NS and one SOA. The only authoritative Samba AD DC is the first one, 
>>> when you join a second DC, it runs the same code that created the 
>>> SOA during the first DCs provision and because the SOA already 
>>> exists, it fails.
>>> Rowland
>> Yikes! Are you saying DC's with directory integrated zones are not 
>> authoritative for them? That means a NS record needs to be created 
>> manually for each DC added.
> Yes, that's about the size of it. no matter how many DCs you join, you 
> only have one NS, the original DC.
> I have been trying to alter the code, but I am struggling to get 
> another NS record added during the join, it doesn't help that I have 
> no idea what a windows DC SOA record looks like, does each DC have a 
> separate SOA record? or is it like the Samba SOA record and there is 
> only one with multiple NS records?
> Rowland
Each DC should contain only one SOA. This by default is the DC that 
originally created it. Samba currently does it correctly by creating 
just the one during provision.

This is what a Windows SOA should look like.

@   IN  SOA     nameserver.example.microsoft.com.  postmaster.example.microsoft.com. (
                                1            ; serial number
                                3600         ; refresh   [1h]
                                600          ; retry     [10m]
                                86400        ; expire    [1d]
                                3600 )       ; min TTL   [1h]


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