To avoid any timeouts or bumps in DNS resolving using Bind9 under Linux it is recommended to switch off support for ip6.
There are a few things to be done in a couple of steps:
With Webmin:
Click on "Edit Config File"
Now select the file: /etc/bind/names.conf.options
Add the following:
dnssec-enable no;
filter-aaaa-on-v4 yes;
It should look like:
options {
...
dnssec-validation no;
dnssec-enable no;
filter-aaaa-on-v4 yes;
auth-nxdomain no;
listen-on-v6 { any; };
...
};
Now save and close this file.
It was recommended from another source that the step above would not be enough and that the bind9.service should also be modified:
sudo nano /lib/systemd/system/bind9.service
Change the following line by adding -f -4:
[Service]
...
ExecStart=/usr/sbin/named -f -4 $OPTIONS
...
Save the file and restart the Bind9 DNS server.