Additional Zone Files
There are generally two to three additional zone files with which each DNS server needs to be configured. The first is the hints file, which provides a set of NS and glue records for the root servers, e.g., serving the top of the domain tree. DNS servers access the hints file when a given query cannot be answered from the server's configuration files, forwarding (if configured to forward first) or the server's cache. In most cases, the hints file contains NS and glue records for the Internet root servers which provide delegation referrals to TLD servers to enable traversal down the domain tree to resolve the query. In some environments, internal root servers may be configured as discussed in Chapter 13.
The second set of required zone files enable resolution of the general loopback address, generally 127.0.0.1 and ::1. Zone files for the 1.0.0.127.in-addr.arpa and 1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa zones would simply include the required zone TTL, SOA and NS records along with a PTR record pointing to the host's domain name.
Empty Zones
BIND now provides a set of pre-defined 'empty' zones, which contain on SOA and NS records associated with the server itself on which it is configured. These empty zones, all reverse zones, correspond to IP network addresses that are not globally routable on the Internet, e.g., private addresses, link local, and so on. Empty zones inhibit recursion of queries for these zones by authoritatively resolving them and are only used if a user-defined zone does not exist. The following are the pre-defined empty zones:
10.in-addr.arpa | 127.in-addr.arpa | 254.169.in-addr.arpa | 168.192.in-addr.arpa |
16.172.in-addr.arpa | 17.172.in-addr.arpa | 18.172.in-addr.arpa | 19.172.in-addr.arpa |
20.172.in-addr.arpa | 21.172.in-addr.arpa | 22.172.in-addr.arpa | 23.172.in-addr.arpa |
24.172.in-addr.arpa | 25.172.in-addr.arpa | 26.172.in-addr.arpa | 27.172.in-addr.arpa |
28.172.in-addr.arpa | 29.172.in-addr.arpa | 30.172.in-addr.arpa | 31.172.in-addr.arpa |
2.0.192.in-addr.arpa | D.F.ip6.arpa | 8.E.F.ip6.arpa | 9.E.F.ip6.arpa |
A.E.F.ip6.arpa | B.E.F.ip6.arpa | ||
0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa | |||
1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.ip6.arpa | |||
Options are available to define the default server name and contact name fields of the SOA record which is created for these empty zones, which can also be selectively disabled.