[dns-operations] Why would a recusrive caching server not resolve a CNAME?

[Mohamed Lrhazi]

I am thinking this list is not appropriate for some of my questions...
Could someone suggest a better one, maybe as active and rich, as this one,
but more appropriate for general DNS discussions?

Thanks a lot,
Mohamed.


On Sun, Jul 6, 2014 at 2:02 PM, Mohamed Lrhazi <ml623 at georgetown.edu> wrote:

> We had a little mail outage which turned out to be caused by one of our
> caching DNS servers returning the bellow incomplete reply.
>
> Clearing the cache on the problematic server fixed the issue....
>
> Am thinking it is now impossible for me to find the root cause in this
> instance... but wondering if you guys could hint at what could cause such a
> problem... bugs in the DNS servers involved? temporary misconfig at
> Google's servers? network issue?
>
> The setup is a bit convoluted:
>
> cache server --> resolver cache server --> Internet
>
> The fix was clearing at the first server. so I am guessing at some point
> the resolver gave the incomplete answer.
>
> Thanks a lot,
> Mohamed.
>
> ➜  ~  dig mail.google.com @141.161.100.201
>
> ; <<>> DiG 9.9.5-3-Ubuntu <<>> mail.google.com @141.161.100.201
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 20414
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 5
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 4096
> ;; QUESTION SECTION:
> ;mail.google.com. IN A
>
> ;; ANSWER SECTION:
> mail.google.com. 10213 IN CNAME googlemail.l.google.com.
>
> ;; AUTHORITY SECTION:
> google.com. 96485 IN NS ns2.google.com.
> google.com. 96485 IN NS ns3.google.com.
> google.com. 96485 IN NS ns4.google.com.
> google.com. 96485 IN NS ns1.google.com.
>
> ;; ADDITIONAL SECTION:
> ns3.google.com. 108462 IN A 216.239.36.10
> ns4.google.com. 108462 IN A 216.239.38.10
> ns1.google.com. 108462 IN A 216.239.32.10
> ns2.google.com. 108462 IN A 216.239.34.10
>
> ;; Query time: 22 msec
> ;; SERVER: 141.161.100.201#53(141.161.100.201)
> ;; WHEN: Sun Jul 06 12:42:09 EDT 2014
> ;; MSG SIZE  rcvd: 207
>
>
>
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