Multiple AD domains

[Darcy Kevin (FCA)]

Yes, I did misread the original post; thanks for clarifying.

But, the gist of the question seemed to be about mitigating the effects of caching, for dynamically-changing data. At a high level, whether the zones are AD zones or not, whether the “master” is BIND or Microsoft DNS, doesn’t have a whole lot of bearing on that challenge. As should be obvious from what I proposed, I prefer the slaving+NOTIFY approach over setting up fragile forwarding arrangements.

The other sledgehammer approach, of course, is to set the TTLs really low, but that can have a disastrous effect on performance/capacity, according to how frequently the dynamically-changing names are being queried. Of course, no amount of named.conf tweaking will help to mitigate the effects of caching that occurs on the clients themselves (e.g. “nscd” on some *nix platforms, Windows resolver cache for Windows). The only standards-based solution for that is to lower the TTLs. (Non-standards-based solutions include ugly stuff like running a script on every client to flush the cache every minute, ugh). But, as always, lowering TTLs, should be done, if at all, with one’s eyes open to the performance/capacity impact.

                                                                                                                                                                                                                                - Kevin



[FCA_Pantone_email]
----------------------------------------------------------------------
Kevin Darcy
NAFTA Information Security Projects

FCA US LLC
1075 W Entrance Dr,
Auburn Hills, MI 48326
USA

Telephone: +1 (248) 838-6601
Mobile: +1 (810) 397-0103
Email: kevin.darcy at fcagroup.com

From: Chris Buxton [mailto:clists at buxtonfamily.us]
Sent: Thursday, July 28, 2016 12:52 PM
To: Darcy Kevin (FCA)
Cc: bind-users at lists.isc.org
Subject: Re: Multiple AD domains

The OP's question was about setting up BIND, not MS DNS, related to using Samba, not Windows, as the domain controller.

Regards,
Chris

Sent from my iPhone

On Jul 27, 2016, at 12:36 PM, Darcy Kevin (FCA) <kevin.darcy at fcagroup.com<mailto:kevin.darcy at fcagroup.com>> wrote:
My preference? Have all your clients use BIND to resolve DNS (this gives access to more advanced features like sortlisting, good query logging, blacklisting/redirection through the RPZ mechanism, Anycast, etc.). Set up the BIND instances as slaves for the AD zones, and have the AD folks add the BIND instances to the apex NS records so that the DCs will trigger fast replication to BIND via the NOTIFY extension to the protocol.

I’d never let a regular PC client use Microsoft DNS for resolving DNS. Perish the thought!

Note that this approach, if implemented simply, doesn’t scale to large numbers of BIND instances (because you don’t want to add dozens or hundreds of apex NS records to the zone). Beyond a certain threshold, you’d want to set up a multi-level slaving/NOTIFY hierarchy on the BIND side…

                                                                                                                                                                                                                - Kevin



<image001.jpg>
----------------------------------------------------------------------
Kevin Darcy
NAFTA Information Security Projects

FCA US LLC
1075 W Entrance Dr,
Auburn Hills, MI 48326
USA

Telephone: +1 (248) 838-6601
Mobile: +1 (810) 397-0103
Email: kevin.darcy at fcagroup.com<mailto:kevin.darcy at fcagroup.com>

From: bind-users [mailto:bind-users-bounces at lists.isc.org] On Behalf Of Jeff Sadowski
Sent: Wednesday, July 27, 2016 3:00 PM
To: bind-users at lists.isc.org<mailto:bind-users at lists.isc.org>
Subject: Re: Multiple AD domains

should I setup 192.168.1.1 as slaves to these two domains would that fix it?

On Wed, Jul 27, 2016 at 12:56 PM, Jeff Sadowski <jeff.sadowski at gmail.com<mailto:jeff.sadowski at gmail.com>> wrote:
On the samba mailing list they described setting up the DC as the NS and forward to another machine for more rules.
This will work fine for one domain. Now lets say I have 2 domains.

If I setup forwarders like so on 192.168.1.1

zone "domainA" IN { type forward; forward only; forwarders { 192.168.2.1; }; };
zone "domainB" IN { type forward; forward only; forwarders { 192.168.3.1; }; };

It will cache entries for each domain and if a computer gets a different address for dhcp it will update on the domain's DNS but the dns on 192.168.1.1 will have a cached entry untill it expires.

192.168.2.1 and 192.168.3.1 are setup to forward all other zones than their domain names to 192.168.1.1

if I have DNS server set for all machines in domainA to 192.168.2.1 all machines on domainA see any DNS changes to domainA imediately machines on domainB are cached and can take time to clear out.
And
if I have DNS server set for all machines in domainB to 192.168.3.1 all machines on domainB see any DNS changes to domainB imediately machines on domainA are cached and can take time to clear out.

What is the best way to resolve this issue?

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