"multiple RRs of singleon type"
Here is an example syslog error message we received on a BIND 9.x
nameserver when trying to perform a zone transfer from a master zone
with "multiple RRs
of singleton type."
Mar 18 15:36:23 host named[748]: [ID 866145
daemon.error] transfer of 'zone/IN'
from name_server#53: failed
while receiving responses: multiple RRs of singleton type
This error means that zone on
name_server contains more than
one SOA record (unlikely) or multiple CNAME records for a given name
(likely). Either situation is in volation of DNS RFC's.
BIND 9.x servers cannot
be forced to transfer a zone with these errors. BIND 8.x offers a multiple-cnames directive that
allows multiple CNAME records for a given name.
To fix the problem, first confirm that there is not more than one SOA
record for the zone:
dig @name_server zone axfr | grep SOA
If only one SOA record is returned, the problem is likely multiple
CNAME records for a given name.
Generate a list of multiple CNAMEs:
for CNAME in `dig @name_server zone
axfr | grep CNAME | awk '{print $1}' | sort | uniq -d`
do
dig @name_server zone axfr | grep
"^$CNAME"
done
An easy way to identify multiple CNAMES is with the h2n utility:
h2n -V zone 2>&1 | grep
"already exists as a CNAME"
Example:
host.example.com.
14400 IN CNAME
host1.example.com.
host.example.com.
14400 IN CNAME
host2.example.com.
These multiple CNAME records can be rewritten as multiple A records
(using IP addresses instead of hostnames) to achieve "load-balancing"
and
RFC compliance:
host.example.com.
14400 IN A
IP_address_of_host1.example.com.
host.example.com.
14400 IN A
IP_address_of_host2.example.com.
The records have to be modified on name_server's
zone
file in order to fix the "multiple RRs of singleton type" errors.
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Last modified: 09/20/2004