[Samba] which DNS backend ?

mathias dufresne infractory at gmail.com
Tue Mar 1 10:07:02 UTC 2016

2016-02-28 23:42 GMT+01:00 Reindl Harald <h.reindl at thelounge.net>:

> Am 28.02.2016 um 23:10 schrieb Rowland penny:
>> On 28/02/16 21:56, Reindl Harald wrote:
>>> Am 28.02.2016 um 22:22 schrieb John Gardeniers:
>>>> Thanks Rowland. Perhaps because I expected these basic issues to have
>>>> been resolved long ago I never thought to check the SOA records. You are
>>>> perfectly correct - the second DC is not listed
>>> since when is more than one NS listed in the SOA?
>>> http://rscott.org/dns/soa.html
>>> MNAME ("Primary NS") - This entry is the domain name of the name
>>> server that was the original source of the data (this entry MUST be
>>> your primary nameserver). This is your primary nameserver, and MUST be
>>> the one and only server that you ever update. You must not update the
>>> secondary server(s) -- they will update automatically, based on this
>>> the SOA record. Problem? This should be a fully qualified domain name .
>>> OK, I see where you are coming from, but, this is referring to a normal
>> dns server that replicates to other secondary dns servers. AD dns works
>> a little differently, all AD dns servers replicate dns records to each
>> other and each AD DC is supposed to be authoritative for the dns domain,
>> this does not happen if your first DC goes down when you are using the
>> internal dns server. As an aside, my first DC shutdown for some reason,
>> I didn't notice for a couple of hours, until I tried to 'ssh' into it, I
>> didn't notice because *everything* else just kept working on my second DC
> well, that's not the business of the SOA record
> it's a matter of NS-records
NS: name servers. Servers which can be used to ask for IP address for a
specified zone. They are authoritative (meaning their replies are the right
replies, they are the authority.)

Note about NS: this knid of record is not used by clients but only by DNS
servers. When a client need to find an IP it sends DNS name to configured
DNS server. This configured DNS server look into its own zones, tries to
resolve the name and, sometimes, forward the query to upper DNS servers.
For me the only moment where NS record are used is that very specific kind
of request.
Ex: client wants to resolve intranet.ibm.li, client send request to
configured-DNS-server for intranet.ibm.li.
Configured-DNS-server is not able to resolve that name, the
configured-DNS-server must find NS for ibm.li.
Configured-DNS-server send request to ROOT server for .li, asking for NS
for ibm.li zone.
Configured-DNS-server receives list of NS for ibm.li, use one of them to
send request for intranet.ibm.li to one of these DNS which are
authoritative for ibm.li.

SOA: start of authority. All name servers for a zone are authoritative, for
answers. With standard Bind and standard DNS config, only DNS server is
declared as master. This master can modify the zone _file_. This zone
_file_ is pushed from master to slaves. SOA is DNS server which can modify
the zone content.

As explained Rowland, in AD all DNS servers can modify the zone content.
All DNS server which can modify the zone is SOA. So in AD all DNS servers
are SOA.



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