[Samba] Samba4 with external bind - best practices?

mathias dufresne infractory at gmail.com
Tue Aug 9 08:39:27 UTC 2016 

A reverse zone is a zone as others. Configure the reverse(s) zone(s) as you
do for standard zones.

A:
Clients -> main DNS (Bind, not Samba, not DC) -> AD DNS servers

Clients know only your company's DNS server, not AD DNS servers. This name
server (the clients resolver) will send AD DNS request to AD DNS server
because of the forward zone (type forward).

B:
Clients -> AD DNS servers -> main DNS (Bind, not Samba, not DC)

Clients must be reconfigured (a bad point imho, I'm lazy) to use Samba DNS
servers as resolver.
You must also make a choice on which DC would be used to do that job if you
have more than 2 DC (with 2 DC you can set both as resolver on clients).
Samba must be configured using "dns forwarder = 192.168.0.1" where
192.168.0.1 would be your company's DNS server.

tcpdump is a very great tool to understand DNS behaviour which is not so
complex for what we generally need.
tcpdump -i eth0 port domain host <ip of client>
would be sufficient to see what happens when a client tries to resolve
something. This tcpdump could be run on the client's resolver: you will see:
- client request arriving
- forwarding request according to your own configuration if needed
- answer from others DNS servers
- answer send back to the client
All you need to make it clear ;)


2016-08-05 18:07 GMT+02:00 Elias Pereira <empbilly at gmail.com>:

> mathias, I believe I get it. :D
>
> The "A" option can be "resolved" with the inclusion of the zone that you
> suggested me, right?
>
> zone "ad.domain.tld" IN {
>>   type forward;
>>   forward only;
>>   forwarders {
>>     <ip of 1st DC>;
>>     <ip of 2nd DC>;
>>     ....
>>     <ip of Nth DC>;
>>   };
>> };
>
>
> And in the "B" option I set up in "DNS DC" each zone belonging to the "DNS
> non-DC"?
>
> E.g:
>
>> zone "domain.tld" {
>>     type forward;
>>     type forward;
>>     forward only;
>>         forwarders {
>>             <ip of DNS non-DC>;
>>     };
>> };
>
>
> The reverse zones also will be this way?
>
> E.g:
>
>> zone "0.168.192.in-addr.arpa" {
>>     type forward;
>>     type forward;
>>     forward only;
>>         forwarders {
>>             <ip of DNS non-DC>;
>>     };
>> };
>
>
> Sorry for so many questions, but maybe this will help others who are
> having the same doubts. Thanks again!
>
> On Fri, Aug 5, 2016 at 7:02 AM, mathias dufresne <infractory at gmail.com>
> wrote:
>
>> You do what you want!
>>
>> The point is the clients must resolve everything.
>>
>> You have two options:
>> A - client resolver is non-DC DNS server: here the non-DC DNS server must
>> be configured to forward DNS requests about AD to AD DNS servers (to DCs)
>> B - client resolver is AD DNS server: here AD DNS server(s) used as
>> resolver(s) must be configured to forward any non-AD DNS request to non-DC
>> DNS server.
>>
>> Hoping this is clear enough...
>>
>> Cheers,
>>
>> mathias
>>
>> 2016-08-04 21:34 GMT+02:00 Elias Pereira <empbilly at gmail.com>:
>>
>>> Guys,
>>>
>>> In the clients dns settings I configure the Samba4 or external DNS IP?
>>>
>>> On Thu, Jul 28, 2016 at 5:57 AM, mathias dufresne <infractory at gmail.com>
>>> wrote:
>>>
>>>> Here we (the DNS team of our company, not me ;) chose the zone type
>>>> forward
>>>> as it is the way DNS works (one resolver on client system, this resolver
>>>> will forward requests to others DNS server to get answer) and also
>>>> because
>>>> that seemed to them the strongest against failure: there is no data
>>>> stored
>>>> on the client resolver, there can't be corrupted data on this DNS server
>>>> when with masters / slaves slaves have to wait for synchronization, they
>>>> host data, these data can be corrupted... in addition of the very same
>>>> problems on any masters...
>>>> And we can declare as much zone with type forward as we want so it works
>>>> also with multiple domains, AD or not.
>>>>
>>>> 2016-07-27 21:02 GMT+02:00 Jeff Sadowski <jeff.sadowski at gmail.com>:
>>>>
>>>> > Looking over this thread it got me thinking of multiple domains and
>>>> then
>>>> > thinking maybe it would be better to setup the external DNS as a
>>>> slave to
>>>> > the AD domain?
>>>> >
>>>> > Then you could have it resolve from the external DNS for multiple AD
>>>> > domains.
>>>> >
>>>> > On Wed, Jul 27, 2016 at 9:32 AM, Elias Pereira <empbilly at gmail.com>
>>>> wrote:
>>>> >
>>>> > > I found this article about separate samba4 and bind.
>>>> > >
>>>> > >
>>>> > https://quercerjanath.wordpress.com/samba-active-directory-w
>>>> ith-bind9-on-separate-machines-ubuntu-14-04/
>>>> > >
>>>> > > Em 27/07/2016 9:39 AM, "mathias dufresne" <infractory at gmail.com>
>>>> > escreveu:
>>>> > >
>>>> > > > 2016-07-26 13:16 GMT+02:00 Rowland penny <rpenny at samba.org>:
>>>> > > >
>>>> > > > > On 26/07/16 09:31, mathias dufresne wrote:
>>>> > > > >
>>>> > > > >> Hi Elias,
>>>> > > > >>
>>>> > > > >> Separating DNS and AD services:
>>>> > > > >> It should be possible to have AD DNS server hosted on a non-DC
>>>> > server.
>>>> > > > >> Samba Wiki explain we just have to include
>>>> > > > >> "/var/lib/samba/private/named.conf" in Bind configuration.
>>>> This
>>>> > > library
>>>> > > > >> can
>>>> > > > >> be replaced be one of those shipped with Bind, this library
>>>> will
>>>> > need
>>>> > > > >> configuration for it can deal with remote DC(s).
>>>> > > > >> Please note I never tried that, 'cause I'm a lazy guy, but that
>>>> > should
>>>> > > > be
>>>> > > > >> possible: Bind+DLZ seems to me to be meant for that kind of
>>>> job.
>>>> > > > >>
>>>> > > > >> One (or more) non-DC DNS server dealing with AD DNS servers:
>>>> > > > >> That is more simple to achieve:
>>>> > > > >> - just configure AD DNS service as you want (please note that
>>>> few
>>>> > > weeks
>>>> > > > >> ago
>>>> > > > >> Samba's internal DNS server was still not able to work as
>>>> > > multi-masters
>>>> > > > >> which is needed to avoid SPOF in AD, so IMHO the only valid DNS
>>>> > > backend
>>>> > > > is
>>>> > > > >> bind+DLZ if you want high availability)
>>>> > > > >> - add a new zone to your existing DNS server (the one which is
>>>> not
>>>> > AD
>>>> > > > DC)
>>>> > > > >> like that one:
>>>> > > > >>
>>>> > > > >>
>>>> > > >
>>>> > >
>>>> > ------------------------------------------------------------
>>>> ----------------------------------
>>>> > > > >> zone "ad.domain.tld" IN {
>>>> > > > >>    type forward;
>>>> > > > >>    forward only;
>>>> > > > >>    forwarders {
>>>> > > > >>      <ip of 1st DC>;
>>>> > > > >>      <ip of 2nd DC>;
>>>> > > > >>      ....
>>>> > > > >>      <ip of Nth DC>;
>>>> > > > >>    };
>>>> > > > >> };
>>>> > > > >>
>>>> > > > >>
>>>> > > >
>>>> > >
>>>> > ------------------------------------------------------------
>>>> ----------------------------------
>>>> > > > >> Restart your external non-DC Bind service and it should be
>>>> able to
>>>> > > > resolve
>>>> > > > >> one more zone: the one from your AD.
>>>> > > > >> What is nice in that is you don't need to take in account
>>>> _msdcs
>>>> > zone
>>>> > > as
>>>> > > > >> it
>>>> > > > >> is a sub zone of "ad.domain.tld", your external Bind will also
>>>> > forward
>>>> > > > >> requests regarding _msdcs to AD servers.
>>>> > > > >>
>>>> > > > >> I did not played with that for a relatively long time and I'm
>>>> just
>>>> > > > coming
>>>> > > > >> back from vacations, so I'm not sure if you would need to allow
>>>> > > > forwarding
>>>> > > > >> and recursion on that non-DC DNS server. It could be
>>>> necessary...
>>>> > > Anyway
>>>> > > > >> as
>>>> > > > >> this DNS should be meant to resolve Internet addresses in
>>>> addition
>>>> > of
>>>> > > > your
>>>> > > > >> local domain(s) recursion and forwarding should be accepted
>>>> > already...
>>>> > > > >>
>>>> > > > >> Hoping this clarify DNS management a little bit and that helps
>>>> you,
>>>> > > > >>
>>>> > > > >> Mathias
>>>> > > > >>
>>>> > > > >>
>>>> > > > >>
>>>> > > > >>
>>>> > > > > The Samba wiki page:
>>>> > > > >
>>>> > > https://wiki.samba.org/index.php/Configure_BIND_as_backend_f
>>>> or_Samba_AD
>>>> > > > >
>>>> > > > > Has these lines:
>>>> > > > >
>>>> > > > >  * Since the BIND DLZ module accesses the AD database directly,
>>>> BIND
>>>> > > > >    for AD zones must be on the same machine.
>>>> > > > >
>>>> > > >
>>>> > > > This, for me, means: as long as we use the BIND DLZ module
>>>> provided by
>>>> > > > Samba, Bind must run on same host as Samba AD DC".
>>>> > > > In other words, you should be able to move Bind to another host
>>>> if, as
>>>> > I
>>>> > > > said yesterday, you accept to use standard module (so not Samba's
>>>> Bind
>>>> > > > module) and configure it correctly. Of course this is more
>>>> complicated
>>>> > to
>>>> > > > achieve, especially compared to the forward zone I described also
>>>> > > > yesterday.
>>>> > > >
>>>> > > >
>>>> > > > >  * Because the BIND DLZ module uses the information already
>>>> stored in
>>>> > > > >    AD, you do not need to create any extra databases.
>>>> > > > >
>>>> > > > > Or to put it another way, if you want to use bind_dlz, you must
>>>> run
>>>> > > Bind9
>>>> > > > > on the DC and you do not need to create any zones (except the
>>>> reverse
>>>> > > > zone
>>>> > > > > and you have to do this anyway)
>>>> > > > >
>>>> > > > > Rowland
>>>> > > > >
>>>> > > > > --
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>>>> the
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>>>> > > > >
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>>>
>>>
>>>
>>> --
>>> Elias Pereira
>>>
>>
>>
>
>
> --
> Elias Pereira
>

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