Strange problem with a query deleting a record...

John E.P. Hynes johnh at
Sat Aug 24 12:55:57 UTC 2013

On 08/24/2013 12:46 AM, Barry Margolin wrote:
> In article <mailman.1159.1377301811.20661.bind-users at>,
>   Mark Andrews <marka at> wrote:
>> In message <52177D81.8020206 at>, Kevin Darcy writes:
>>> On 8/22/2013 12:55 PM, johnh at wrote:
>>>> Greetings All,
>>>> First of all, I apologize if this is out of place - I'm having a very
>>>> strange issue that is either a problem with bind itself, or at least,
>>>> affecting it.  Summary:
>>>> For only ONE address, whenever I attempt to access it through my squid
>>>> proxy, the record disappears from DNS, and the retry time changes too.
>>>> Essentially, accessing works, but a link to a portal
>>>> on
>>>> that page to the subdomain causes the problem.  I'm
>>>> willing to bet the problem lies with squid, but as to how it could
>>>> possibly change a record in bind... Well, I'm stumped.  If you don't go
>>>> through squid, everything works.  All other requests to bind for the
>>>> address of the host in question work fine. Here's a the output of dig
>>>> from
>>>> before accessing the page through squid:
>>>> ; <<>> DiG 9.4.1-P1 <<>>
>>>> ;; global options:  printcmd
>>>> ;; Got answer:
>>>> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 45037
>>>> ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0
>>>> ;            IN      A
>>>>     17      IN      A       111.222.333.123
>>>>         168319  IN      NS
>>>>         168319  IN      NS
>>>> ;; Query time: 0 msec
>>>> ;; SERVER:
>>>> ;; WHEN: Thu Aug 22 12:29:57 2013
>>>> ;; MSG SIZE  rcvd: 88
>>>> You can do anything to request the address from bind and it works,
>>>> *except* try to access it through squid.  Bypassing squid and going
>>>> directly through the firewall works fine.
>>>> Now, immediately after you try to access it through squid:
>>>> ; <<>> DiG 9.4.1-P1 <<>>
>>>> ;; global options:  printcmd
>>>> ;; Got answer:
>>>> ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 43943
>>>> ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
>>>> ;            IN      A
>>>>         298     IN      SOA
>>>> 2006062510 3600 3600 2592000 300
>>>> ;; Query time: 0 msec
>>>> ;; SERVER:
>>>> ;; WHEN: Thu Aug 22 12:30:06 2013
>>>> ;; MSG SIZE  rcvd: 95
>>>> After the 5-minute retry shown above expires, the original record
>>>> reappears.
>>>> Ideas?  I'm stumped.  It seems like squid is somehow able to corrupt
>>>> bind's info, but I can't imagine how.
>>> I have a theory. If this is a name that's hosted on a stupid
>>> load-balancer, and that load-balancer doesn't understand non-A-record
>>> query types, then if Squid is sending a non-A query type (e.g. SRV,
>>> possibly even AAAA, if it's *really* stupid), then the load-balancer may
>>> be erroneously "poisoning" your cache with an NXDOMAIN response.
>>> We ran into this many years ago with Cisco GSSes (Global Site Selectors)
>>> and work around it by having a "shadow" version of the zone, which the
>>> GSSes proxy to for QTYPEs they don't handle. That "shadow" version of
>>> the zone has a wildcard entry in it which forces responses to be NODATA
>>> instead of NXDOMAIN, and this prevents the cache poisoning.
>>>                                                               - Kevin
>> The load balancer should be able to correct for such misconfigurations
>> by changing the rcode of the response from NXDOMAIN to NOERROR.  It
>> knows what names is is answering for so it can know that the NXDOMAIN
>> is a erroneous response.
> If I understand what Kevin was saying, the load balancer IS the DNS
> server. If you ask it for the A record it's responsible for, it sends a
> reasonable reply. If you ask it for some other record type for that
> name, it sends NXDOMAIN instead of NOERROR.
> It's a design flaw in these load balancers.

Thanks everyone who's been helping with this.

In order to investigate this further, I did a tcpdump of both a 
"working" conversation of a browser requesting the site, not going 
through the squid proxy, and another of the "broken" conversation 
through the proxy.

Result:  There is an NXDOMAIN response to a request for an AAAA record 
that the proxy makes that is causing this.  The browser never asks for 
anything but an A record, which succeeds.

I've contacted the site in question with this info, so hopefully it'll 
get resolved.  I'll keep the list posted on any results or info for 


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