RE: Forwarding from delegated zone not working

[Darcy Kevin (FCA)]

You can certainly configure the subdomains that way, but the same resolver 
which followed the subdomain.example.com delegation in the first place, to your 
BIND instance, will presumably follow the delegation of 
sub.subdomain.example.com (as it is published via NS records in the parent 
zone) to find the nameservers for that subzone, query them, and expect 
authoritative responses. Your forwarding config won't be used, by such a 
resolver, since it'll be sending you non-recursive (RD=0) queries, which are 
incompatible with forwarding.

Ultimately, the bottom line is that if the "leaf-node" data is not available in 
an authoritative form, then you can't use delegation alone to facilitate its 
resolution. You'd need to set up some sort of forwarding, possibly multi-hop 
forwarding, which is notorious for being fragile, inefficient and lacking in 
scalability.

You mentioned in another post that the DNS data in question is for a cloud 
environment. My experience so far (primarily with AWS) is that these cloud 
providers don't understand how robust DNS enterprise architectures work. If 
they did, they would have offered authoritative, replicate-able DNS zone data 
as a basic service, straight out of the gate. Supposedly this "feature" is "on 
the roadmap" for AWS, but it seems to be a distant goal, with no particular 
priority. In the meantime, they are requiring their enterprise customers to 
sacrifice some of the reliability and performance we've built up in our DNS 
infrastructures over years (and, in some cases, decades), instead stringing 
together forwarding hierarchies and other nonsense like that.

(Editorial note: I originally got carried away at this point, explaining my 
model of how DNS is, conceptually, constructed -- authoritative core, inner 
iterative-resolution layer, outer recursive-resolution layer -- along with a 
diatribe about how poor/junior enterprise DNS architects try, with sub-optimal 
results, to build on recursive resolution as a foundation, because that's the 
only layer they really understand. But I don't want to put anyone to sleep, or 
fill up their mailboxes with walls of text, so I'll forego that for now, saving 
the text for some other day). 

May I ask: why would you put anything non-AD-related, of actual importance, in 
a *subdomain* of an Active Directory zone ? Maybe it's just a matter of 
perspective, but I see Active Directory as just one service we run in our 
enterprise, among many. So, while it gets its own namespace, it doesn't get to 
control the *main* namespace -- certainly, we would never put anything 
non-AD-related *underneath* an AD zone. Granted, I don't know your 
organization's structure, internal politics, history, etc. But it just seems 
rather odd to me that you're delegating stuff from an AD zone. I view such 
namespaces as "leaves", not "branches".


- Kevin


-Original Message-
From: bind-users [mailto:bind-users-boun...@lists.isc.org] On Behalf Of 
seanliam73
Sent: Wednesday, October 11, 2017 3:45 AM
To: bind-users@lists.isc.org
Subject: RE: Forwarding from delegated zone not working

Thanks Kevin

That is what I suspected. If I make the delegated server the master/slave for 
the sub-domain that has been delegated, could I then set up forward zones for 
further sub-domains? i.e

subdomain.example.com (delegated domain set as master zone) 
sub.subdomain.example.com (forward zone)

Sean



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RE: Forwarding from delegated zone not working

[seanliam73]

Thanks Kevin

That is what I suspected. If I make the delegated server the master/slave
for the sub-domain that has been delegated, could I then set up forward
zones for further sub-domains? i.e

subdomain.example.com (delegated domain set as master zone)
sub.subdomain.example.com (forward zone)

Sean



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Re: Forwarding from delegated zone not working

[seanliam73]

Unfortunately we don't manage the AD server, that has been outsourced.

The team that manage AD have delegated the subdomain to our bind 9 instance
which in turn has a number of forwarding zones configured. This is to manage
DNS over a number of cloud based environments.



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Re: Forwarding from delegated zone not working

[Bob Harold]

On Tue, Oct 10, 2017 at 11:21 AM, seanliam73  wrote:

> Hi
>
> I have a subdomain delegated from AD to a bind9 instance I have running
> that
> so that all requests for that subdomain are sent to the bind 9 instance. I
> would then like to set up zone forwarding so that further subdomains can be
> managed by other bind 9 instances.
>
> I know the forwarding is working because I can query the main bind9
> instance
> at receive the expected results. However if I query from the AD server that
> is doing the delegation I get a SERVFAIL error.
>
> Am I trying to do something that is not possible or am I just missing some
> configuration.
>
> *main instance config*
>
> options {
> directory "/var/named";
> listen-on port 53 { listen addr; };
> auth-nxdomain yes;
> recursion yes;
> allow-query { ip addresses; };
>

- You might also need to add:
   allow-recursion { ip addresses; };

-- 
Bob Harold


> listen-on-v6 { any; };
> dnssec-enable no;
> dnssec-validation no;
> dnssec-lookaside auto;
> };
>
> logging {
> channel default_debug {
> file "data/named.run";
> severity debug 3;
> };
>
> channel querylog {
> file "data/query.log";
> severity debug 5;
> };
>
> category default { default_debug; };
> category queries { querylog; };
> };
>
> zone "example.company.com" IN {
> type forward;
> forward only;
> forwarders { ip address; };
> };
>
> zone "development.example.company.com" IN {
> type forward;
> forward only;
> forwarders { ip address; };
> };
>
>
>
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RE: Forwarding from delegated zone not working

[Ben Croswell]

I guess i made the assumption that zone was properly forwarded at the MS
end.

 However as you mentioned if it was only delegated then it would SERVFAIL
at the BIND server when receiving an iterative query from MS if BIND isn't
authoritative.

On Oct 10, 2017 11:44 AM, "Darcy Kevin (FCA)" <kevin.da...@fcagroup.com>
wrote:

But surely you’d get an NXDOMAIN in that case, not a SERVFAIL.



The assumption I made in my post was that the delegation was pointed to the
forwarding BIND instance, which is a non-starter.



-  Kevin





*From:* bind-users [mailto:bind-users-boun...@lists.isc.org] *On Behalf Of *Ben
Croswell
*Sent:* Tuesday, October 10, 2017 11:38 AM
*To:* seanliam73 <sean.orei...@landg.com>
*Cc:* bind-users@lists.isc.org
*Subject:* Re: Forwarding from delegated zone not working



If the AD environment loads company.com you need to make sure it has NS
delegations. The nameserver will ignore the zone forwarded if it knows the
child doesn't exist.



On Oct 10, 2017 11:22 AM, "seanliam73" <sean.orei...@landg.com> wrote:

Hi

I have a subdomain delegated from AD to a bind9 instance I have running that
so that all requests for that subdomain are sent to the bind 9 instance. I
would then like to set up zone forwarding so that further subdomains can be
managed by other bind 9 instances.

I know the forwarding is working because I can query the main bind9 instance
at receive the expected results. However if I query from the AD server that
is doing the delegation I get a SERVFAIL error.

Am I trying to do something that is not possible or am I just missing some
configuration.

*main instance config*

options {
directory "/var/named";
listen-on port 53 { listen addr; };
auth-nxdomain yes;
recursion yes;
allow-query { ip addresses; };
listen-on-v6 { any; };
dnssec-enable no;
dnssec-validation no;
dnssec-lookaside auto;
};

logging {
channel default_debug {
file "data/named.run";
severity debug 3;
};

channel querylog {
file "data/query.log";
severity debug 5;
};

category default { default_debug; };
category queries { querylog; };
};

zone "example.company.com" IN {
type forward;
forward only;
forwarders { ip address; };
};

zone "development.example.company.com" IN {
type forward;
forward only;
forwarders { ip address; };
};



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Re: Forwarding from delegated zone not working

[Tony Finch]

seanliam73  wrote:
>
> I know the forwarding is working because I can query the main bind9
> instance at receive the expected results. However if I query from the AD
> server that is doing the delegation I get a SERVFAIL error.

I guess one possible cause for this problem might be if the AD server is
making iterative queries (RD=0) rather than recursive queries (RD=1). In
this the BIND forwarding setup will not work because forwarding only
applies to recursive queries.

It's probably more reliable to set up the subdomain and sub-sub-domains
with proper delegations, so that normal iterative resolution works.

A few unrelated notes...

> options {
> directory "/var/named";
> listen-on port 53 { listen addr; };
> auth-nxdomain yes;

Don't use this option, it has been useless since 2001.

> recursion yes;
> allow-query { ip addresses; };
> listen-on-v6 { any; };
> dnssec-enable no;

There should not be any reason to turn off DNSSEC support.

> dnssec-validation no;
> dnssec-lookaside auto;

dnssec-lookaside is now obsolete, but even before it was decommissioned
these two lines contradicted each other!

> };

Tony.
-- 
f.anthony.n.finch    http://dotat.at/  -  I xn--zr8h punycode
Lundy, Fastnet, Irish Sea, Southeast Shannon: Southwesterly 5 to 7,
occasionally gale 8 later. Slight or moderate, becoming moderate or rough.
Occasional rain. Moderate or good, occasionally poor.
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RE: Forwarding from delegated zone not working

[Darcy Kevin (FCA)]

But surely you’d get an NXDOMAIN in that case, not a SERVFAIL.

The assumption I made in my post was that the delegation was pointed to the 
forwarding BIND instance, which is a non-starter.


-  Kevin


From: bind-users [mailto:bind-users-boun...@lists.isc.org] On Behalf Of Ben 
Croswell
Sent: Tuesday, October 10, 2017 11:38 AM
To: seanliam73 <sean.orei...@landg.com>
Cc: bind-users@lists.isc.org
Subject: Re: Forwarding from delegated zone not working

If the AD environment loads company.com<http://company.com> you need to make 
sure it has NS delegations. The nameserver will ignore the zone forwarded if it 
knows the child doesn't exist.

On Oct 10, 2017 11:22 AM, "seanliam73" 
<sean.orei...@landg.com<mailto:sean.orei...@landg.com>> wrote:
Hi

I have a subdomain delegated from AD to a bind9 instance I have running that
so that all requests for that subdomain are sent to the bind 9 instance. I
would then like to set up zone forwarding so that further subdomains can be
managed by other bind 9 instances.

I know the forwarding is working because I can query the main bind9 instance
at receive the expected results. However if I query from the AD server that
is doing the delegation I get a SERVFAIL error.

Am I trying to do something that is not possible or am I just missing some
configuration.

*main instance config*

options {
directory "/var/named";
listen-on port 53 { listen addr; };
auth-nxdomain yes;
recursion yes;
allow-query { ip addresses; };
listen-on-v6 { any; };
dnssec-enable no;
dnssec-validation no;
dnssec-lookaside auto;
};

logging {
channel default_debug {
file "data/named.run";
severity debug 3;
};

channel querylog {
file "data/query.log";
severity debug 5;
};

category default { default_debug; };
category queries { querylog; };
};

zone "example.company.com<http://example.company.com>" IN {
type forward;
forward only;
forwarders { ip address; };
};

zone "development.example.company.com<http://development.example.company.com>" 
IN {
type forward;
forward only;
forwarders { ip address; };
};



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RE: Forwarding from delegated zone not working

[Darcy Kevin (FCA)]

It doesn't work to delegate to a forwarder; you have to delegate to something 
that's authoritative for the zone (master or slave). Delegated nameservers are 
expected to have a full copy of the zone, either as the source (master) or 
through replication (slave).

Now, if you have restrictions/limitations that prevent you both from a) 
delegating directly from AD to the authoritative nameservers, and b) 
replicating from the authoritative nameservers to the BIND instance in 
question, then you'd need to look into some sort of "DNS proxy", but that's not 
BIND, and really beyond the scope of this list.


- Kevin

-Original Message-
From: bind-users [mailto:bind-users-boun...@lists.isc.org] On Behalf Of 
seanliam73
Sent: Tuesday, October 10, 2017 11:22 AM
To: bind-users@lists.isc.org
Subject: Forwarding from delegated zone not working

Hi

I have a subdomain delegated from AD to a bind9 instance I have running that so 
that all requests for that subdomain are sent to the bind 9 instance. I would 
then like to set up zone forwarding so that further subdomains can be managed 
by other bind 9 instances.

I know the forwarding is working because I can query the main bind9 instance at 
receive the expected results. However if I query from the AD server that is 
doing the delegation I get a SERVFAIL error.

Am I trying to do something that is not possible or am I just missing some 
configuration.

*main instance config* 

options {
directory "/var/named";
listen-on port 53 { listen addr; };
auth-nxdomain yes;
recursion yes;
allow-query { ip addresses; };
listen-on-v6 { any; };
dnssec-enable no;
dnssec-validation no;
dnssec-lookaside auto;
};

logging {
channel default_debug {
file "data/named.run";
severity debug 3;
};

channel querylog {
file "data/query.log";
severity debug 5;
};

category default { default_debug; };
category queries { querylog; };
};

zone "example.company.com" IN {
type forward;
forward only;
forwarders { ip address; };
};

zone "development.example.company.com" IN {
type forward;
forward only;
forwarders { ip address; };
};



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Re: Forwarding from delegated zone not working

[Ben Croswell]

If the AD environment loads company.com you need to make sure it has NS
delegations. The nameserver will ignore the zone forwarded if it knows the
child doesn't exist.

On Oct 10, 2017 11:22 AM, "seanliam73"  wrote:

> Hi
>
> I have a subdomain delegated from AD to a bind9 instance I have running
> that
> so that all requests for that subdomain are sent to the bind 9 instance. I
> would then like to set up zone forwarding so that further subdomains can be
> managed by other bind 9 instances.
>
> I know the forwarding is working because I can query the main bind9
> instance
> at receive the expected results. However if I query from the AD server that
> is doing the delegation I get a SERVFAIL error.
>
> Am I trying to do something that is not possible or am I just missing some
> configuration.
>
> *main instance config*
>
> options {
> directory "/var/named";
> listen-on port 53 { listen addr; };
> auth-nxdomain yes;
> recursion yes;
> allow-query { ip addresses; };
> listen-on-v6 { any; };
> dnssec-enable no;
> dnssec-validation no;
> dnssec-lookaside auto;
> };
>
> logging {
> channel default_debug {
> file "data/named.run";
> severity debug 3;
> };
>
> channel querylog {
> file "data/query.log";
> severity debug 5;
> };
>
> category default { default_debug; };
> category queries { querylog; };
> };
>
> zone "example.company.com" IN {
> type forward;
> forward only;
> forwarders { ip address; };
> };
>
> zone "development.example.company.com" IN {
> type forward;
> forward only;
> forwarders { ip address; };
> };
>
>
>
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