Bind unable to get MX reocrd from Parrent name server

[Matus UHLAR - fantomas]

On 05.07.13 12:59, Fosiul Alam wrote:
>I am not the domain admin for "rbcaa.co.za"
>I can see they have issue with their domain setup .
>but what I want to know is :
>when all Dns server can resolved their mx record example ,
>mxtoolbox,introdns,google .. (Despite they have issue with their dns
>setup for that domain (as you said) ) then why we cant ??

because some kinds of DNS problems, especially this one (incosistent NS
between parent zone delegation and the zone itself) often lead to this kind
of issues. 

In your example, the NS servers in the zone rbcaa.co.za refuse queries for
the zone, so any server that caches the NS records will fail as long.

The reason why services like mxtoolbox work is that they apparently do not
behave as standard (rfc-conforming) DNS clients, they trace those domains to
catch those issues. For example:

http://www.intodns.com/rbcaa.co.za

clearly says there are ERRORS in the domain. I really do not think that this
should be interpreted as "they can resolve". Other DNS checker also says:

     No name servers found at child.

     Not enough nameserver information was found to test the zone
     rbcaa.co.za, but an IP address lookup succeeded in spite of that.

http://dnscheck.iis.se/?time=1373027394&id=3521288&view=basic&test=standard

>>> rbcaa.co.za. 86400 IN NS ns1.yithosting.co.za.
>>> rbcaa.co.za. 86400 IN NS ns2.yithosting.co.za.
>>> ;; Received 108 bytes from 196.4.160.17#53(196.4.160.17) in 81 ms
>>>
>>> rbcaa.co.za. 14400 IN A 41.203.1.156
>>> rbcaa.co.za. 86400 IN NS demeter.is.co.za.
>>> rbcaa.co.za. 86400 IN NS babylon.mitsol.co.za.
>>> ;; Received 99 bytes from 41.203.1.158#53(41.203.1.158) in 41 ms

% dig any rbcaa.co.za. @babylon.mitsol.co.za.

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> any rbcaa.co.za.
; @babylon.mitsol.co.za.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 40276
;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

% dig +norec any rbcaa.co.za. @babylon.mitsol.co.za.

; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> +norec any rbcaa.co.za.
; @babylon.mitsol.co.za.
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 52980
;; flags: qr; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0


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