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IT Interview Questions:What is the "in-addr.arpa" zone used for?
Information Technology (IT) Interview Questions and Answers
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IT Interview Questions:What is the "in-addr.arpa" zone used for?
In a Domain Name System (DNS) environment, it is common for a user or an
application to request a Reverse Lookup of a host name, given the IP address.
This article explains this process. The following is quoted from RFC 1035:
"The Internet uses a special domain to support gateway location and Internet
address to host mapping. Other classes may employ a similar strategy in other
domains. The intent of this domain is to provide a guaranteed method to
perform host address to host name mapping, and to facilitate queries to
locate all gateways on a particular network on the Internet. "The domain
begins at IN-ADDR.ARPA and has a substructure which follows the Internet
addressing structure. "Domain names in the IN-ADDR.ARPA domain are defined to
have up to four labels in addition to the IN-ADDR.ARPA suffix. Each label
represents one octet of an Internet address, and is expressed as a character
string for a decimal value in the range 0-255 (with leading zeros omitted
except in the case of a zero octet which is represented by a single zero).
"Host addresses are represented by domain names that have all four labels
specified." Reverse Lookup files use the structure specified in RFC 1035. For
example, if you have a network which is 150.10.0.0, then the Reverse Lookup
file for this network would be 10.150.IN-ADDR.ARPA. Any hosts with IP
addresses in the 150.10.0.0 network will have a PTR (or 'Pointer') entry in
10.150.IN- ADDR.ARPA referencing the host name for that IP address. A single
IN- ADDR.ARPA file may contain entries for hosts in many domains. Consider
the following scenario. There is a Reverse Lookup file 10.150.IN-ADDR.ARPA
with the following contents: Exp : 1.20 IN PTR WS1.ACME.COM.
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