servfail only for a zone

[Lucio Crusca]

Hello,

I have two nameservers, the master and its slave, and they work ok for 
several zones. However for one of the zones (aquilacorde.com), the slave 
replies with SERVFAIL, and I don't understand why.

The master is ns1.virtualbit.it, the slave is ns2.virtualbit.it.

I've tried enabling debug output for ns2, but in the logs I get nothing 
useful (or nothing I can understand). Here is what I get in the logs 
when I try

$ dig @ns2.virtualbit.it aquilacorde.com

----8x-------

# tail -f /var/log/syslog | grep named
...
Jul 13 19:10:46 apps named[25270]: client 74.125.187.80#33867 
(aquilacorde.com): query: aquilacorde.com IN MX -EDC (136.243.232.143)
Jul 13 19:10:46 apps named[25270]: client 74.125.187.80#33867 
(aquilacorde.com): query failed (SERVFAIL) for aquilacorde.com/IN/MX at 
query.c:5813
Jul 13 19:10:46 apps named[25270]: client 74.125.187.80#42506 
(aquilacorde.com): query: aquilacorde.com IN MX -EDC (136.243.232.143)
Jul 13 19:10:46 apps named[25270]: client 74.125.187.80#42506 
(aquilacorde.com): query failed (SERVFAIL) for aquilacorde.com/IN/MX at 
query.c:5813
Jul 13 19:10:46 apps named[25270]: client 74.125.187.82#59535 
(aquilacorde.com): query: aquilacorde.com IN MX -C (136.243.232.143)
Jul 13 19:10:46 apps named[25270]: client 74.125.187.82#59535 
(aquilacorde.com): query failed (SERVFAIL) for aquilacorde.com/IN/MX at 
query.c:5813
...

And here is the aquilacorde.com zonefile at the master ns1:

$TTL    3600
@       IN      SOA     ns1.virtualbit.it. info.aquilacorde.com. (
                             2015070601         ; Serial
                       1200         ; Refresh
                     180         ; Retry
                             3600         ; Expire
                      3600)        ; Default TTL
;
@       IN      NS      ns1.virtualbit.it.
@    IN    NS    ns2.virtualbit.it.
aquilacorde.com.             IN      MX       1 aspmx.l.google.com.
aquilacorde.com.             IN      MX       5 alt1.aspmx.l.google.com.
aquilacorde.com.             IN      MX       5 alt2.aspmx.l.google.com.
aquilacorde.com.         IN      MX       10 alt3.aspmx.l.google.com.
aquilacorde.com.             IN      MX       10 alt4.aspmx.l.google.com.
aquilacorde.com.    IN    A    136.243.232.141
new        IN    A    136.243.232.141
www        IN    A    136.243.232.141
www2        IN    A    136.243.232.141
ftp        IN    A    136.243.232.141
beta        IN    A    136.243.232.141
shop        IN    A    136.243.232.141
ricerche        IN      A       136.243.232.141
old             IN      A       195.138.240.116
start           IN    CNAME    ghs.google.com.
sites           IN      CNAME   ghs.google.com.
mail            IN      CNAME   ghs.google.com.
calendar        IN      CNAME   ghs.google.com.
docs            IN      CNAME   ghs.google.com.
googlec4e941738b3160fb IN CNAME google.com.

What's wrong?