As 10.in-addr.arpa is private namespace *all* of you recursive servers should 
be configured to serve it.  This is similar to how all of your recursive 
nameservers know where the root servers are except you are using a slave zone 
instead of a hint zone.

i.e.

10.in-addr.arpa {
        type slave;
        masters { <address of AD server>; };
        file “slave/10.in-addr.arpa”;// adjust to match your local conventions.
        request-ixfr no;             // only use AXFR for 10.in-addr.arpa as it 
is coming from AD as IXFR does not work well.
        forwarders { /* empty */ };  // use iterative resolution for the 
children of 10.in-addr.arpa.
};

Forwarding should NEVER be needed if servers are reachable at the IP level.  If 
the solution says “configure a forward zone” it is almost always wrong.

Do the similar for the top of all other private namespaces you are using.

Mark

> On 4 Apr 2020, at 03:06, bind-li...@iano.org wrote:
> 
> Hi,
> 
> In summary, my question is whether there is a way to configure a bind caching 
> server to provide recursion in response to iterative queries for records in a 
> forward type zone.
> 
> The background is that we have:
> 
> - AD domain controllers that are authoritative for all of 10.in-addr.arpa. in 
> our data centers - most clients point to these for DNS resolution.
> - Linux bind caching resolvers in our data centers - domain controllers 
> forward to these for anything they don’t own.
> - Some AWS VPCs which have been allocated subdomains of 10.in-addr.arpa. and 
> are routable from our data centers. These have Route53 inbound endpoints 
> which answer queries for those subdomains.
> - The bind caching resolvers have forwarding rules for those subdomains to 
> the AWS inbound endpoints.
> 
> The subdomains in our AWS VPCs have NS records, but the servers those point 
> to refuse queries for records in the subdomains. The zone resolution is taken 
> care of by the Route53 resolver service. The Route53 inbound endpoints 
> successfully resolve queries from our data centers for those subdomains as 
> long as the recursion desired flag is set to 1 in the query. If recursion 
> desired is set to 0 they do not send any reply at all.
> 
> We want to be able to resolve PTR records in the subdomains in the AWS VPCs 
> from our data centers where, as I said above, the clients point to the domain 
> controllers for DNS resolution.
> 
> Because the AD domain controllers already own 10.in-addr.arpa, they refuse to 
> allow us to configure conditional forwarding for its subdomains. So we 
> delegated the subdomains to the inbound endpoints. Because they are 
> delegations, the domain controllers set the recursion desired flag to 0 on 
> the queries they send to the endpoints, and we are not getting replies from 
> the endpoints.
> 
> As a workaround we tried delegating to our linux bind caching resolvers but 
> we ran into the same issue, that the domain controllers set recursion desired 
> to 0. As a result, when our linux caching servers have the result in cache, 
> the lookup is successful, but when it would require a fresh lookup it gets a 
> reply with no answers. Hence my question, is there a way to tell our bind 
> caching resolvers to ignore the recursion desired flag and provide recursion 
> anyway?
> 
> Thanks,
> Maria
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-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: ma...@isc.org

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