Re: Google DNS Oddity

[Warren Kumari <warren () kumari net>]

Yes, this is no longer occurring / is resolved.

Apologies,
W

On Mon, Sep 9, 2019 at 1:37 PM Florian Brandstetter via NANOG <
nanog () nanog org> wrote:

> Unable to replicate this in London:
>
> ```
> ; <<>> DiG 9.11.5-P1-1ubuntu2.5-Ubuntu <<>> @ns1.google.com.
> www.google.com. aaaa
> ; (2 servers found)
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61970
> ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
> ;; WARNING: recursion requested but not available
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;www.google.com.                        IN      AAAA
> ;; ANSWER SECTION:
> www.google.com.         300     IN      AAAA    2a00:1450:4009:80d::2004
> ```
>
> going by the latency, ns1.google.com
> <https://link.getmailspring.com/link/C27D5EBE-B680-425A-B057-218C6300A7B4 () getmailspring 
> com/0?redirect=ns1.google.com&recipient=bmFub2dAbmFub2cub3Jn>
> travels to NL from our UK PoPs though:
>
> ```
> Host                              Loss%   Snt   Last   Avg  Best  Wrst
> StDev
> 1. ???
> 2. ???
> 3. ae26-0.ebr01.lon3.uk.globalone  0.0%    13    2.1   6.2   1.0  45.7
> 12.9
> 4. 2001:7f8:4::3b41:1              0.0%    13    0.7   0.8   0.6   1.7
> 0.4
> 5. 2001:4860:0:1101::10            0.0%    13    0.7   2.7   0.7  14.2
> 4.2
> 6. 2001:4860::c:4000:cf5b          0.0%    13    1.8   2.1   1.5   4.0
> 0.7
> 7. 2001:4860::8:4000:d325          0.0%    13    8.6   7.3   6.6   9.5
> 0.9
> 8. 2001:4860::22:4001:70b          0.0%    13    6.4   9.5   6.4  36.9
> 8.3
> 9. 2001:4860:0:1::be7             23.1%    13    7.3   7.5   7.3   7.7
> 0.1
> 10. ???
> 11. ???
> 12. ???
> 13. ???
> 14. ???
> 15. ???
> 16. ???
> 17. ???
> 18. ???
> 19. ns1.google.com                  0.0%    12    6.4   6.4   6.3   6.5
> 0.0
> ```
> On Sep. 6 2019, at 9:49 pm, Stephen Stuart <stuart () tech org> wrote:
>
> Do you see the same behavior when you execute your dig query without
> the trailing dot?
>
> Thanks,
> Stephen
>
> On Sep 6, 2019, at 3:11 PM, Chip Marshall via NANOG <nanog () nanog org>
> wrote:
>
> Hello, I'm seeing an oddity when doing DNS lookups for www.google.com
> from our
> London datacenter, and I'm curious if other people are seeing the same
> behavior.
>
> It appears that when we ask for www.google.com. we sometimes get an answer
> that only contains records for www-anycast.google.com., which our resolver
> ignores as they don't match the query.
>
> As seen with dig:
>
> ```
> # dig @ns1.google.com. www.google.com. aaaa
>
> ; <<>> DiG 9.10.3-P4-Ubuntu <<>> @ns1.google.com. www.google.com. aaaa
> ; (2 servers found)
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42641
> ;; flags: qr aa rd; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 1
> ;; WARNING: recursion requested but not available
>
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags:; udp: 512
> ;; QUESTION SECTION:
> ;www.google.com. IN AAAA
>
> ;; ANSWER SECTION:
> www-anycast.google.com. 300 IN AAAA 2001:4860:4802:34::75
> www-anycast.google.com. 300 IN AAAA 2001:4860:4802:38::75
> www-anycast.google.com. 300 IN AAAA 2001:4860:4802:36::75
> www-anycast.google.com. 300 IN AAAA 2001:4860:4802:32::75
>
> ;; Query time: 7 msec
> ;; SERVER: 216.239.32.10#53(216.239.32.10)
> ;; WHEN: Fri Sep 06 19:05:32 UTC 2019
> ;; MSG SIZE rcvd: 167
> ```
>
> So far I've observed this with A and AAAA queries. It's my understanding
> that
> without a CNAME record in the answer, the resolver is doing the right
> thing by
> ignoring the answer, as there's no linkage between www and www-anycast.
>
> Is this broken, or is this just some weird DNS trick I've not come across
> before?
>
>
> You may want to post on dns-operations instead.
>
> Can you do a dig +trace www.google.com instead, that would be more
> instructive about whatт€™s happening at each layer o
>
> f the delegation.
>
>
> - Jared
>
> [image: Sent from Mailspring]



-- 
I don't think the execution is relevant when it was obviously a bad idea in
the first place.
This is like putting rabid weasels in your pants, and later expressing
regret at having chosen those particular rabid weasels and that pair of
pants.
   ---maf