<div dir="ltr"><div>
<span class="gmail-tlid-translation gmail-translation" lang="en"><span title="" class="gmail-">As for Viettel, I don't know how they configure it.</span><br><span title="" class="gmail-">But when I use a server on another network, the result is as follows:</span></span>
</div><div><br></div><div>; <<>> DiG 9.6-ESV-R8 <<>> @1<span style="background-color:rgb(255,255,0)">15.84.177.8 250.0-24.199.212.125.in-addr.arpa ptr</span></div>; (1 server found)<br>;; global options: +cmd<br>;; Got answer:<br>;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52626<br>;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 3, ADDITIONAL: 0<br>;; WARNING: recursion requested but not available<br><br>;; QUESTION SECTION:<br>;250.0-24.199.212.125.in-addr.arpa. IN PTR<br><br><span style="background-color:rgb(255,255,0)">;; ANSWER SECTION:<br>250.0-24.199.212.125.in-addr.arpa. 360 IN PTR <a href="http://smtp.vss.gov.vn">smtp.vss.gov.vn</a>.<br>250.0-24.199.212.125.in-addr.arpa. 360 IN PTR <a href="http://baohiemxahoi.gov.vn">baohiemxahoi.gov.vn</a>.</span><br><br>;; AUTHORITY SECTION:<br>199.212.125.in-addr.arpa. 360 IN NS <a href="http://ns.viettelidc.com.vn">ns.viettelidc.com.vn</a>.<br>199.212.125.in-addr.arpa. 360 IN NS <a href="http://ns1.viettelidc.com.vn">ns1.viettelidc.com.vn</a>.<br>199.212.125.in-addr.arpa. 360 IN NS <a href="http://ns2.viettelidc.com.vn">ns2.viettelidc.com.vn</a>.<br><br>;; Query time: 26 msec<br>;; SERVER: 115.84.177.8#53(115.84.177.8)<br>;; WHEN: Fri Aug 21 09:18:35 2020<br><div>;; MSG SIZE rcvd: 175</div><div><br></div><div>Chinhlk<br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Vào Th 4, 19 thg 8, 2020 vào lúc 22:25 Matus UHLAR - fantomas <<a href="mailto:uhlar@fantomas.sk">uhlar@fantomas.sk</a>> đã viết:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">>> On 20 Aug 2020, at 00:41, Matus UHLAR - fantomas <<a href="mailto:uhlar@fantomas.sk" target="_blank">uhlar@fantomas.sk</a>> wrote:<br>
>><br>
>>> On Wed, Aug 19, 2020 at 7:42 AM Matus UHLAR - fantomas<br>
>>> <<a href="mailto:uhlar@fantomas.sk" target="_blank">uhlar@fantomas.sk</a>> wrote:<br>
>>>> again, why you query for 250.0-24.199.212.125.in-addr.arpa<br>
>>>> under normal circumstances there's no point of querying that name.<br>
>><br>
>> On 19.08.20 10:05, tale via bind-users wrote:<br>
>>> Well yes and no. While an individual user would typically not,<br>
>>> resolvers sure will. While trying to resolve<br>
>>> 250.199.212.125.in-addr.arpa, it will eventually get to<br>
>>> 250.199.212.125.in-addr.arpa CNAME 250.0-24.199.212.125.in-addr.arpa.<br>
>><br>
>> my question is why would anyone do this, as this apparently does not make<br>
>> sense.<br>
<br>
On 20.08.20 00:59, Mark Andrews wrote:<br>
>Presumably because they don’t know that APNIC can delegate the /24s that make<br>
>up the /17 independently of each other.<br>
<br>
even if not, they can fetch whole /24 from their customer (requiring<br>
customer to add their NSes as long).<br>
<br>
but, yes, in case of very incompetent customer they can require such<br>
delegation.<br>
<br>
<br>
>> someone (vietel) illogically delegated whole /24 subnet to broken servers:<br>
>><br>
>> 199.212.125.in-addr.arpa. 86400 IN NS <a href="http://dns2.vietel.com.vn" rel="noreferrer" target="_blank">dns2.vietel.com.vn</a>.<br>
>> 199.212.125.in-addr.arpa. 86400 IN NS <a href="http://dns1.vietel.com.vn" rel="noreferrer" target="_blank">dns1.vietel.com.vn</a>.<br>
>><br>
>> 0.199.212.125.in-addr.arpa has address 125.235.4.59<br>
>> 1.199.212.125.in-addr.arpa is an alias for 1.0-24.199.212.125.in-addr.arpa.<br>
>> ...<br>
>> 255.199.212.125.in-addr.arpa is an alias for 255.0-24.199.212.125.in-addr.arpa.<br>
<br>
delegation from apnic to vietel:<br>
<br>
199.212.125.in-addr.arpa. 86400 IN NS <a href="http://dns2.vietel.com.vn" rel="noreferrer" target="_blank">dns2.vietel.com.vn</a>.<br>
199.212.125.in-addr.arpa. 86400 IN NS <a href="http://dns1.vietel.com.vn" rel="noreferrer" target="_blank">dns1.vietel.com.vn</a>.<br>
199.212.125.in-addr.arpa. 3600 IN NSEC 2.212.125.in-addr.arpa. NS RRSIG NSEC<br>
199.212.125.in-addr.arpa. 3600 IN RRSIG NSEC 13 5 3600 20200917160047 20200818150047 30887 125.in-addr.arpa. 5ixPuj/J+cDFSDwxy3MSMs1xkmpGrdzhrmjiodo6CkEBazwUxojGfIYU R5MNZCbDoMZEF4Fq8eL9lcsZgrBctA==<br>
;; Received 321 bytes from 203.119.95.53#53(<a href="http://ns2.apnic.net" rel="noreferrer" target="_blank">ns2.apnic.net</a>) in 255 ms<br>
<br>
delegation from vietel to vietelidc:<br>
<br>
0-24.199.212.125.in-addr.arpa. 86400 IN NS <a href="http://ns.viettelidc.com.vn" rel="noreferrer" target="_blank">ns.viettelidc.com.vn</a>.<br>
0-24.199.212.125.in-addr.arpa. 86400 IN NS <a href="http://ns2.viettelidc.com.vn" rel="noreferrer" target="_blank">ns2.viettelidc.com.vn</a>.<br>
0-24.199.212.125.in-addr.arpa. 86400 IN NS <a href="http://ns1.viettelidc.com.vn" rel="noreferrer" target="_blank">ns1.viettelidc.com.vn</a>.<br>
;; Received 160 bytes from 203.113.188.2#53(<a href="http://dns2.vietel.com.vn" rel="noreferrer" target="_blank">dns2.vietel.com.vn</a>) in 367 ms<br>
<br>
<br>
zone 199.212.125.in-addr.arpa. at vietelidc who is supposed to provide<br>
0-24.199.212.125.in-addr.arpa:<br>
<br>
199.212.125.in-addr.arpa. 2560 IN SOA <a href="http://ns.viettelidc.com.vn" rel="noreferrer" target="_blank">ns.viettelidc.com.vn</a>. hostmaster.199.212.125.in-addr.arpa. 1597850355 16384 2048 1048576 2560<br>
;; Received 129 bytes from 115.84.181.10#53(<a href="http://ns2.viettelidc.com.vn" rel="noreferrer" target="_blank">ns2.viettelidc.com.vn</a>) in 291 ms<br>
<br>
<br>
vietelidc is in this case the problem:<br>
<br>
1. they block DNS over TCP<br>
2. they should have configured zone 0-24.199.212.125.in-addr.arpa<br>
<br>
although it's possible that <a href="http://viettelidc.com.vn" rel="noreferrer" target="_blank">viettelidc.com.vn</a> asked <a href="http://vietel.com.vn" rel="noreferrer" target="_blank">vietel.com.vn</a> to delegate 199.212.125.in-addr.arpa.<br>
and <a href="http://vietel.com.vn" rel="noreferrer" target="_blank">vietel.com.vn</a> messed it up...<br>
<br>
<br>
<br>
-- <br>
Matus UHLAR - fantomas, <a href="mailto:uhlar@fantomas.sk" target="_blank">uhlar@fantomas.sk</a> ; <a href="http://www.fantomas.sk/" rel="noreferrer" target="_blank">http://www.fantomas.sk/</a><br>
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</blockquote></div>