Let’s say you have two name servers in your closed intranet: ns1.company.com at IP address 10.1.1.1 and ns2.company.com at IP address 10.2.2.2. Configure both name servers as root name servers and, at the same time, as name servers for the company.com domain.

You will need to insert a line in the /etc/named.boot file of the ns1.company.com and ns2.company.com servers. This line will declare that your name server is also the primary name server for the root domain ‘.’:

...
primary company.com file1
primary . file2
...

Note that, there is no line containing the cache command.

It is important to check file2, which specifies the root domain:

@ IN SOA ...
IN NS ns1.company.com.
IN NS ns2.company.com.
company.com IN NS ns1.company.com.
IN NS ns2.company.com.
ns1.company.com. IN A 10.1.1.1
ns2.company.com. IN A 10.1.1.1

In this file, we have not inserted any NS resource record for other domains than company.com. That is why there...