サーバーがドメインに対して権限を持っているにもかかわらず、BIND DNSサーバー構成でAUTHORITYフラグが0に設定された応答を受け取るのはなぜですか？

https://fedoramagazine.org/how-to-setup-a-dns-server-with-bind/

この記事では、バインディングでDNSサーバーを設定しました。

Master=192.168.1.206=master.example.com
Client=192.168.1.3=client.example.com

//
// /etc/named.conf
//
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
//
// See /usr/share/doc/bind*/sample/ for example named configuration files.
//

options {
    #listen-on port 53 { 127.0.0.1; 192.168.1.2; };
    #listen-on-v6 port 53 { ::1; };
    directory   "/var/named";
    dump-file   "/var/named/data/cache_dump.db";
    statistics-file "/var/named/data/named_stats.txt";
    memstatistics-file "/var/named/data/named_mem_stats.txt";
    secroots-file   "/var/named/data/named.secroots";
    recursing-file  "/var/named/data/named.recursing";
    allow-query     { localhost; 192.168.1.0/24; };

    /* 
     - If you are building an AUTHORITATIVE DNS server, do NOT enable recursion.
     - If you are building a RECURSIVE (caching) DNS server, you need to enable 
       recursion. 
     - If your recursive DNS server has a public IP address, you MUST enable access 
       control to limit queries to your legitimate users. Failing to do so will
       cause your server to become part of large scale DNS amplification 
       attacks. Implementing BCP38 within your network would greatly
       reduce such attack surface 
    */
    recursion yes;

    #dnssec-validation yes;

    managed-keys-directory "/var/named/dynamic";
    geoip-directory "/usr/share/GeoIP";

    pid-file "/run/named/named.pid";
    session-keyfile "/run/named/session.key";

    /* https://fedoraproject.org/wiki/Changes/CryptoPolicy */
    include "/etc/crypto-policies/back-ends/bind.config";
};

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

zone "." IN {
    type hint;
    file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

zone "example.com" IN {
type master;
file "forward";
allow-update { none; };
};

zone "1.168.192.in-addr.arpa" IN {
type master;
file "reverse";
allow-update { none; };
};

このように、順方向および逆方向ゾーンファイルを設定しました。

#forward

$TTL 86400
@   IN  SOA     master.example.com. admin.example.com. (
                2023010401  ;Serial
                3600        ;Refresh
                1800        ;Retry
                604800      ;Expire
                86400       ;Minimum TTL
)

@               IN      NS      master.example.com.
@           IN  A       192.168.1.206
@           IN  A       192.168.1.3
@           IN  A       192.168.1.4
master          IN  A       192.168.1.206
webserver       IN  A       192.168.1.4

#reverse

$TTL 86400
@   IN  SOA     master.example.com. admin.example.com. (
                2023010401  ;Serial
                3600        ;Refresh
                1800        ;Retry
                604800      ;Expire
                86400       ;Minimum TTL
)

@               IN  NS      master.example.com.
@           IN  PTR     example.com.
master          IN  A       192.168.1.206
webserver       IN  A       192.168.1.4
206         IN  PTR     master.example.com.
4           IN  PTR     webserver.example.com.

その後、/etc/resolv.confメインサーバーに設定しました。

search example.com
nameserver 192.168.1.206

今マスターに行きましょう。

dig example.com

答えを受けましたが、受け取りました。AUTHORITY=0

[root@dns01 named]# dig example.com

; <<>> DiG 9.16.23-RH <<>> example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55501
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
; COOKIE: b15240d00532152a010000006623f6970bb37622180b1f28 (good)
;; QUESTION SECTION:
;example.com.            IN      A

;; ANSWER SECTION:
example.com.     86400   IN      A       192.168.1.3
example.com.     86400   IN      A       192.168.1.206
example.com.     86400   IN      A       192.168.1.4

;; Query time: 0 msec
;; SERVER: 192.168.1.206#53(192.168.1.206)
;; WHEN: Sat Apr 20 18:08:39 WEST 2024
;; MSG SIZE  rcvd: 123