DNS Reverse Name Resolution Using the IN-ADDR.ARPA Domain
(Page 3 of 4)
Resource Record Setup for Reverse Resolution
With the IN-ADDR.ARPA structure in place, we can now associate one entry in this name space with each entry in the real DNS name space. We do this using the PTR (pointer) resource record type. For example, if www.xyzindustries.com has the IP address 220.127.116.11, then the DNS server for its zone will have an address resource record indicating this. In master file text format, it will say something like this:
www.xyzindustries.com. A 18.104.22.168
However, there will also be the following entry for it within the IN-ADDR.ARPA domain:
22.214.171.124.IN-ADDR.ARPA PTR www.xyzindustries.com
(Remember that DNS names are case-insensitive, so the IN-ADDR.ARPA could also be given as in-addr.arpa).
Once this is done, reverse name resolution can be easily performed by doing a name resolution on 126.96.36.199.in-addr.arpa. If we do this, a server for the IN-ADDR.ARPA domain will return to us the name www.xyzindustries.com. This is also shown in Figure 246.
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