The pseudodomain in-addr.arpa is used for the reverse lookup of IP addresses
into hostnames. It is appended to the network part of the address in reverse notation.
So 192.168 is resolved into 168.192.in-addr.arpa. See Example 25.7, “Re-
verse Lookup” (page 442).
Example 25.7
Reverse Lookup
1. $TTL 2D
2. 168.192.in-addr.arpa. IN SOA dns.example.com. root.example.com. (
3. 2003072441 ; serial
4. 1D ; refresh
5. 2H ; retry
6. 1W ; expiry
7. 2D ) ; minimum
8.
9. IN NS dns.example.com.
10.
11. 1.5 IN PTR gate.example.com.
12. 100.3 IN PTR www.example.com.
13. 253.2 IN PTR cups.example.com.
Line 1:
$TTL denes the standard TTL that applies to all entries here.
Line 2:
The conguration le should activate reverse lookup for the network 192.168.
Given that the zone is called 168.192.in-addr.arpa, it should not be added
to the hostnames. Therefore, all hostnames are entered in their complete form—with
their domain and with a "." at the end. The remaining entries correspond to those
described for the previous example.com example.
Lines 3–7:
See the previous example for example.com.
Line 9:
Again this line species the name server responsible for this zone. This time,
however, the name is entered in its complete form with the domain and a "." at
the end.
Lines 11–13:
These are the pointer records hinting at the IP addresses on the respective hosts.
Only the last part of the IP address is entered at the beginning of the line, without
442 Reference
