[Freeipa-users] Still unclear about relation between IPA DNS domain and company DNS domain.

[Brian Candler]

On 07/12/2016 08:58, freeIPA users list wrote:
> On ke, 07 joulu 2016, List dedicated to discussions about use, 
> configuration and deployment of the IPA server. wrote:
>> I know the Quick Start Guide and Deployment Recommendations cover 
>> this in
>> depth, but there are still some ambiguities.
>>
>> I'm trying to figure out if a company like us, lautus.net should use 
>> a DNS
>> subdomain like ipa.lautus.net for the IPA domain, or not.
> It is really depending on your deployment details.
>
> If you already have some other Kerberized environment in place and you
> are not going to replace it by FreeIPA, then you need to make sure that
> new FreeIPA deployment would not conflict with the existing one.
Or if you think there's a chance you might want to add another 
Kerberized environment later (e.g. "ad.lautus.net")

>
>> should continue to be hosted by DNS servers elsewhere that delegate say,
>> ipa.lautus.net to FreeIPA.
The question of whether you host ipa.lautus.net DNS (or indeed 
lautus.net DNS) in FreeIPA is a different issue.

If you're happy with your existing DNS infrastructure, then you can 
either delegate ipa.lautus.net to your FreeIPA servers (with NS 
records); or run FreeIPA without DNS, and simply import the 
ipa.lautus.net SRV records directly into the lautus.net domain.

Having FreeIPA host the ipa.lautus.net domain means these SRV records 
are populated automatically, but it's not really that hard to add them 
to an existing DNS service.

OTOH, if you *don't* already have a good authoritative internal DNS 
service with a UI that you like, then you might want to use FreeIPA for 
this anyway. You can easily create extra zones in FreeIPA.

I would be a bit wary about putting FreeIPA servers out on the public 
Internet though. For one thing, the default config is an open resolver 
(which you can tighten easily enough). I also have a deep distrust of 
Java, but maybe that's just me.


>
>> But on the other hand the same doc is full of examples where a Kerberos
>> realm like EXAMPLE.COM (instead of IPA.EXAMPLE.COM) is used, i.e example
>> 2.2. of secion 2.3.4. But the same guide also says that the Kerberos 
>> realm
>> should be the same as the ipa DNS domain, just uppercased. So example 
>> 2.2.
>> implies that example.com is running their DNS domain on FreeIPA, for
>> everything, not just for IPA SRV and TXT entries.
The Kerberos realm always has a corresponding DNS domain, so realm 
IPA.LAUTUS.NET has a corresponding DNS domain "ipa.lautus.net".

But with FreeIPA you can still manage hosts called foo.lautus.net or 
bar.int.lautus.net. At worst you'd have some extra [domain_realm] 
mappings in krb5.conf

(Aside: Active Directory is much more fussy, and basically doesn't work 
if the hosts don't have hostnames within the same DNS domain as their 
kerberos realm - and indeed have reverse DNS as well as forward)

>
>> And when ipa-client-install is run on somehost.lautus.net, it also 
>> defaults
>> to LAUTUS.NET for Kerberos domain, as if the default expectation is that
>> your toplevel company DNS name would be your kerberos domain.
But you can override that.

>
>
>> And when I install a trial IPA server on host ipa-server-1.lautus.net 
>> using
>> "ipa-server-install --setup-dns --realm IPA.LAUTUS.NET --domain
>> ipa.lautus.net --forwarder=8.8.8.8", and then look at the DNS Zones  
>> in the
>> Web UI, I see not only ipa.lautus.net, but also lautus, with record 
>> "@ NS
>> ipa-server-1.lautus.net". In other words the IPA server defaults to
>> thinking it owns the domain above ipa.lautus.net too. Which goes against
>> 2.3.1 above.
Interesting. What does "ipa dnszone-find --pkey-only" show?

It seems like it's created an authoritative zone both for the server's 
own domain (lautus.net if the server is xxx.lautus.net) as well as the 
realm's domain (ipa.lautus.net)

I don't know why it's doing that. Now I've checked with another system 
here: the hostname is "ipa-1.int.example.com" and the realm is 
"ipa.example.com", and you're right, it is authoritative for both:

   Zone name: int.example.com.
   Zone name: ipa.example.com.

This isn't what I wanted. The int.example.com domain is hosted 
externally and I didn't want to override it. Right now it's hiding all 
names in int.example.com that it doesn't know about.

I would expect that it's possible to remove this zone, but I'd need to 
test that doesn't stop other hosts called xxx.int.example.com from joining.

> Yes and no. What you see with "@ NS ..." is a glue record -- you are
> supposed to have a glue record for IPA domain in the upstream domain,
> this is how domain delegation works in DNS world.
Aside: technically that's not a glue record. A glue record is an A or 
AAAA record when the NS record points to a host within the subdomain 
which is being delegated. It is to solve the chicken-and-egg situation 
of how to contact a nameserver for a domain before you've contacted a 
nameserver for the domain.

In your case, if you already have working DNS for lautus.net, then you 
don't want FreeIPA to be authoritative for lautus.net as well.

Regards,

Brian.