Hints for forwarding a subdomain on a authoritative server

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Tom
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Hints for forwarding a subdomain on a authoritative server

Tom
Hi list

Our BIND (9.16.4) is authoritative for zone "example.com". Now I need to
forward a subzone "sub.example.com" to another nameserver instance on
the same server, running for example under port 5353:

A few years ago, this topic was already discussed:
https://lists.isc.org/pipermail/bind-users/2009-April/076156.html

My BIND config looks like this:
================== SCHNIPP ==================
zone "example.com" {
         type master;
         file "master/example.com.hosts";
         };
zone "sub.example.com" {
         type forward;
         forwarders { 127.0.0.1 port 5353; };
         forward only;
         };
================== SCHNAPP ==================

In the zonefile for "example.com" I have a delegation like this (as
described in the post above):

sub.example.com.            IN      NS      subns.example.com.

So, the authoritative server understands not to be responsible for this
zone and forwards the request to the other nameserver.

But: The zone-forwarding is only working, when I enable "recursion" on
the authoritative server. Does this means, that zone-forwarding really
requires recursion? Is there a better way with not enabling recursion
(perhaps with views) to accomplish this?

Many thanks for any hints.

Kind regards,
Tom
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Re: Hints for forwarding a subdomain on a authoritative server

Sten Carlsen

Thanks

Sten

On 6 Jul 2020, at 16.03, Tom <[hidden email]> wrote:

Hi list

Our BIND (9.16.4) is authoritative for zone "example.com". Now I need to forward a subzone "sub.example.com" to another nameserver instance on the same server, running for example under port 5353:

A few years ago, this topic was already discussed:
https://lists.isc.org/pipermail/bind-users/2009-April/076156.html

My BIND config looks like this:
================== SCHNIPP ==================
zone "example.com" {
       type master;
       file "master/example.com.hosts";
       };
zone "sub.example.com" {
       type forward;
       forwarders { 127.0.0.1 port 5353; };
       forward only;
       };
================== SCHNAPP ==================

In the zonefile for "example.com" I have a delegation like this (as described in the post above):

sub.example.com.            IN      NS      subns.example.com.

So, the authoritative server understands not to be responsible for this zone and forwards the request to the other nameserver.

But: The zone-forwarding is only working, when I enable "recursion" on the authoritative server. Does this means, that zone-forwarding really requires recursion?
Yes.
Is there a better way with not enabling recursion (perhaps with views) to accomplish this?
Stub zones are normally recommended instead.

Many thanks for any hints.

Kind regards,
Tom
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Re: Hints for forwarding a subdomain on a authoritative server

Tony Finch
In reply to this post by Tom
Tom <[hidden email]> wrote:
>
> But: The zone-forwarding is only working, when I enable "recursion" on the
> authoritative server. Does this means, that zone-forwarding really requires
> recursion?

Yes, forwarding is completely specific to recursive servers. That is, the
server doing the forwarding must be recursive, and the target server must
also be recursive.

[ In some limited cases you can get away with the target server not being
recursive; I think the restrictions are that the target zone must not have
any delegations or out-of-zone CNAMEs, but I haven't tested this myself. ]

> Is there a better way with not enabling recursion (perhaps with views)
> to accomplish this?

Use a type "static-stub" zone if the target server is authoritative.

If the server doing the forwarding is not recursive then it needs to
secondary its own authoritative copy of the zone. But presumably you are
trying to forward because AXFRing the zone isn't possible. In that case
you need something like dnsdist which can act as a DNS reverse proxy. BIND
won't query another server when a query is RD=0.

Tony.
--
f.anthony.n.finch  <[hidden email]>  http://dotat.at/
Fisher, German Bight: West or northwest 7 or gale 8, occasionally severe gale
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