nettester Examples of such domains are www.dhl.de or whois.denic.de. Running dig with +trace works until it reaches the actual DNS servers responsible for said domains (*.akam.net for www.dhl.de or ns*.denic.net for whois.denic.de) which fail to resolve making it impossible to query them.
Can't reproduce this using the unbound on a recent-ish 9.3_STABLE. All of these resolved fine: www.dhl.de, dhl.de, www.denic.de, denic.de. (The config. file is a stripped down /usr/share/examples/unbound/unbound.conf)
Querying the A-records using host using this script also works:
query-ns.sh
#!/bin/sh
set -eu
me=${0##*/}
die() {
echo >&2 "$me: $*"
exit 1
}
test $# -eq 1 || die "no site-name given"
# Get nameserver list from the WHOIS service.
#
site=$1
ns=$(whois $site | sed 's/\r$//' | while read s1 s2 v junk
do if [ "$s1" = Nserver: ]
then echo $s2
elif [ "$s1" = Name ] && [ "$s2" = Server: ]
then echo $v
fi
done)
test -n "$ns" || die "no nameservers found"
# Lookup A-records for $site and www.$site on each of the NSes.
#
for a in $ns
do host -t A $site $a
echo " ---"
host -t A www.$site $a
echo "----------------------------------------"
done
What does the script print if you run:
./query-ns.sh dhl.de
./query-ns.sh denic.de
It should print the A-records for site and www.site.