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<div class="moz-cite-prefix">On 02/24/2015 10:10 AM, Longina
Przybyszewska wrote:<br>
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cite="mid:84B3E55FE25BE542A37420D946B1372F148F9061@ADM-EXMBX10B.adm.c.sdu.dk"
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<p class="MsoNormal"><span lang="EN-US">Hi,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">We have a problem with
the way SSSD tries to find out where to send DDNS updates.
The problem is that SSSD doesn’t use DNS to find the
authoritative name server for a given zone, but assume that
it must be the Active Directory Domain Controller to which
it is connected.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">In our case this is not
correct in any way.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Our DNS setup is like
this:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">DNS-PTR.example.com is
Authoritative for all our DNS PTR/reverse records
(xxx.in-addr.arpa) and for the forward zone example.com with
the exception of local.example.com (and subdomains), which
is delegated to localserver1.local.example.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">(This is purely internal
– external we have another DNS service let’s call it
DNS-external.example.com, but it doesn’t matter in this
example/problem).<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Our Active directory is
a forrest named local.example.com with subdomains
a.local.example.com, b.local.example.com, etc. each Active
directory subdomain has it’s own domain controllers let’s
say localserverA.a.local.example.com,
localserverB.b.local.example.com, etc.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Active Directory
computer objects (accounts) are located in sub-domains ex.
nfsserverA.a.local.example.com,
nfsclientB.b.local.example.com, etc.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Just for your
information: Active Directory user objects (accounts) are
located in all Active Directory domains – including top
domain local.example.com.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The problem:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">When
nfsserverA.a.local.example.com is trying to update it’s DNS
record it’s sending the update to the Active Directory
Domain Controller localserverA.a.local.example.com, which is
only running Active Directory Services (Domain Controller,
Global Catalog, etc.) and not a DNS service, because it
assumes that the Active Directory Domain Controller also is
running DNS service.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">If SSSD had done a DNS
lookup for the DNS Name Server record for
a.local.example.com it’s told that the DNS Name Server is
localserver1.local.example.com. And if it’s looking for the
responsible DNS name server for the reverse zone
x.y.10.in-addr.arpa. (we are running 10.0.0.0/8 divided into
/24 subnets as our internal IP subnets) it’s told to that
the responsible server is DNS-PTR.example.com (only
accessible from our internal network).
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">PS: I have seen the
comments in
<a class="moz-txt-link-freetext" href="https://lists.fedorahosted.org/pipermail/sssd-users/2014-June/001878.html">https://lists.fedorahosted.org/pipermail/sssd-users/2014-June/001878.html</a>
talking about creating an option in sssd.conf called
something like fallback_dns_master, but I find that very
inflexible and not the right way to go … because, if we move
the DNS service form one server to another we’ll have to
change a lot of local client configuration. Another argument
is that we actually have multiple servers authoritative for
local.example.com and I suppose that it’s only possible to
configure one server in the suggested attribute
“fallback_dns_master”.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:DA">Best,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:DA">Longina<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<br>
Sounds like and RFE. Please file a ticket.<br>
<br>
<pre class="moz-signature" cols="72">--
Thank you,
Dmitri Pal
Sr. Engineering Manager IdM portfolio
Red Hat, Inc.</pre>
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