Why do I get underscore DNS queries when my host is running a recursive server?

[Greg Choules]

Please keep your replies on-list.
This should help you understand its purpose:
https://datatracker.ietf.org/doc/rfc9156/

Cheers, Greg

On Mon, 31 Mar 2025 at 11:12, Champion Xie <xiejieling at gmail.com> wrote:

> Thank you for your information
> by the way how to implement QNAME minimisation with domain names starting
> with an underscore
>
> Greg Choules <gregchoules+bindusers at googlemail.com> 于2025年3月31日周一 18:01写道：
>
>> Hello.
>> The underscore character was an old method for performing QNAME
>> minimisation. Look in the CHANGES file for a note about it and the ARM for
>> more detailed information.
>>
>> BIND 9.14 is five years old and has been unsupported for a long time.
>> Please update to 9.18 or 9.20, which contain many improvements, bug and
>> security fixes.
>>
>> cheers, Greg
>>
>> On Mon, 31 Mar 2025 at 10:47, Champion Xie <xiejieling at gmail.com> wrote:
>>
>>>
>>> [root at rancher03 ~]# dig @localhost  www.baidu.com a
>>>
>>> ; <<>> DiG 9.14.12 <<>> @localhost www.baidu.com a
>>> ; (2 servers found)
>>> ;; global options: +cmd
>>> ;; Got answer:
>>> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35287
>>> ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
>>>
>>> ;; OPT PSEUDOSECTION:
>>> ; EDNS: version: 0, flags:; udp: 4096
>>> ; COOKIE: 74f8bc0ee313592d6a463b2f67ea63d442364be432ee42b2 (good)
>>> ;; QUESTION SECTION:
>>> ;www.baidu.com.                 IN      A
>>>
>>> ;; ANSWER SECTION:
>>> www.baidu.com.          1200    IN      CNAME   www.a.shifen.com.
>>> www.a.shifen.com.       120     IN      A       110.242.70.57
>>> www.a.shifen.com.       120     IN      A       110.242.69.21
>>>
>>> ;; Query time: 2507 msec
>>> ;; SERVER: *127.0.0.1#53(127.0.0.1)*
>>> ;; WHEN: Mon Mar 31 17:43:48 CST 2025
>>> ;; MSG SIZE  rcvd: 132
>>>
>>>
>>> 31-Mar-2025 17:38:31.326 address not available resolving '_.com/A/IN':
>>> 2801:1b8:10::b#53
>>> 31-Mar-2025 17:38:31.326 address not available resolving '_.com/A/IN':
>>> 2001:500:2f::f#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:83eb::30#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:502:8cc::30#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:500:d937::30#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:501:b1f9::30#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:231d::2:30#53
>>> 31-Mar-2025 17:38:31.331 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:a83e::2:30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:eea3::30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:d2d::30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:502:7094::30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:500:856e::30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:502:1ca1::30#53
>>> 31-Mar-2025 17:38:31.332 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:d414::30#53
>>> 31-Mar-2025 17:38:31.333 address not available resolving '_.
>>> baidu.com/A/IN': 2001:503:39c1::30#53
>>> 31-Mar-2025 17:38:32.120 address not available resolving '
>>> www.baidu.com/A/IN': 240e:940:603:4:0:ff:b01b:589a#53
>>> 31-Mar-2025 17:38:32.120 address not available resolving '
>>> www.baidu.com/A/IN': 240e:bf:b801:1002:0:ff:b024:26de#53
>>> 31-Mar-2025 17:38:32.124 address not available resolving '
>>> ns3.baidu.com/AAAA/IN': 2001:501:b1f9::30#53
>>> 31-Mar-2025 17:38:32.125 address not available resolving '
>>> ns3.baidu.com/AAAA/IN': 2001:502:1ca1::30#53
>>> 31-Mar-2025 17:38:33.863 address not available resolving '
>>> www.a.shifen.com/A/IN': 240e:bf:b801:1006:0:ff:b04f:346b#53
>>> 31-Mar-2025 17:38:34.803 address not available resolving '
>>> ns1.a.shifen.com/AAAA/IN': 240e:940:603:a:0:ff:b08d:239d#53
>>>
>>> --
>>> Best Regards!!
>>> champion_xie
>>> --
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>>
>
> --
> Best Regards!!
> champion_xie
>
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