BIND started replying to queries for .com with .COM

Daniel Stirnimann daniel.stirnimann at
Thu Mar 31 19:58:01 UTC 2016

Hi Mike,

When BIND first introduced this Case-Insensitive Response Compression
(See I found out that BIND
zone_name case sensitivity in a zone statement is preferred over name
case sensitivity in the zone itself.

So, you can get a google.COM answer because the zone statement at the
authoritative com name server you were talking to is "COM.".


On 30.03.16 23:21, Mike Bernhardt wrote:
> I think you misunderstood me. I was getting back google.COM even when I
> queried the server using nslookup from a command prompt on my Windows
> desktop. The probe was failing because it is case-sensitive, but that was
> the symptom, not the problem.
> For example:
> Server:
> Address:
> Non-authoritative answer:
> Name:    google.COM
> Addresses:  2607:f8b0:4005:801::200e
> Given that the problem cleared after restarting BIND on its CentOS host, I'd
> say the problem was BIND.
> -----Original Message-----
> From: Mark Andrews [mailto:marka at] 
> Sent: Tuesday, March 29, 2016 5:19 PM
> To: Mike Bernhardt
> Cc: bind-users at
> Subject: Re: BIND started replying to queries for .com with .COM
> Your monitoring probe is broken.
> STD 13 says that that the DNS is case preserving.  The problem is that lots
> of servers aren't case preserving instead they echo back the query case in
> the owner names of records returned which named then records.
> In message <030101d18a06$fa21c8d0$ee655a70$>, "Mike Bernhardt"
> writes:
>> I rebooted one of our BIND VMs this morning. It's running BIND 
>> 9.10.3-P3. We noticed that queries for domains with were 
>> answered with domain.COM with the .COM in capital letters. Other 
>> high-levels like .org were not changed. It caused a monitoring probe 
>> to complain because it wasn't getting back what it asked for.
>> Restarting bind on this server fixed the problem. Any ideas on what 
>> happened, or where to look?
>> _______________________________________________
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> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742                 INTERNET: marka at
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