[RndTbl] help! dns zone delegation wonky for AAAA

Trevor Cordes trevor at tecnopolis.ca
Thu Nov 24 03:54:14 CST 2016

On 2016-11-24 Trevor Cordes wrote:
> Maybe I should now reformulate the crux of my problem as this:
> Can I configure bind to return for all AAAA requests in the local zone
> "I'm authoritative but I don't have the answer" instead of SERVFAIL
> *even if the subzone has been delegated*.  Or even specify a
> delegation for certain records (A & MX) only (not AAAA), though I
> specifically read somewhere that that's impossible on purpose.

Eureka!!  The path you set me out on that led to my above reformulation
led me to some other avenues of google attack.  Two ideas in I found a

First I found this named option:
filter-aaaa-on-v4 (and -v6)
"It is intended to help the transition from IPv4 to IPv6 by not giving
IPv6 addresses to DNS clients unless they have connections to the IPv6
Super description and chart here:

Perfect!!  It did indeed filter AAAA when I tested with names like
google.com.  But it failed for my own problematic sites.

So, I turned on more debugging in named and saw the external NS
responses for the subdomain where giving me:
lame-servers: info: FORMERR resolving ...
then my named would give to me:
query failed (SERVFAIL)

So it wasn't the external NS giving me SERVFAIL, but FORMERR... which
then turned into a SERVFAIL from my command's point of view.

Some more searching armed with new keywords I found:

"The root cause is that the name servers for www.ryanair.com are
misconfigured.  They are returning answers as if they are configured
for ryanair.com (see the SOA record) instead of www.ryanair.com as
can be seen below."

Aha!  Ding!  named was barfing because I had two NS's authoritative for
the same domain and one referencing the other.  Even though I was only
trying to reference the delegated subdomain, named didn't like that
arrangement... but not in general, only as it pertained to non-existent
records.  Weird!  (Would have been easier to debug if it didn't work
for any records at all!)

Crossing my fingers, I changed the external server to break out the
zones (the root zone, and the delegated subzone) into two zone files so
now both BOX1 and BOX2 have very similar zone files with regards to the
handling of the ".out." subdomain... they both just delegate it to the
root zone.  It's like I was running the out subdomain on an entirely
separate box from both root NS's.  Restart, pray, and it works!

host problem gone.  sshd problem gone.  dig results are the same
everywhere I attempt the query.  So the problem was a misconfig on my
part because of this very convoluted example when trying to delegate on
"shared but different" domains.  I hope if anyone else ever has this
problem this thread can help them solve it more easily.

Finally, I guess the filter-aaaa-on-v4 didn't help here because of the
nature of the FORMERR.  I guess named was trying to tell me something.

More information about the Roundtable mailing list