IPv4 Reverse Resolution
Reverse DNS lookups for IPv4 addresses use a reverse IN-ADDR entry in the special domain in-addr.arpa. In this domain, an IPv4 address is represented as a concatenated sequence of four decimal numbers, separated by dots, to which is appended the second level domain suffix .in-addr.arpa. The four decimal numbers are obtained by splitting the 32-bit IPv4 address into four 8-bit portions and converting each 8-bit portion into a decimal number. These decimal numbers are then concatenated in the order: least significant 8-bit portion first (leftmost), most significant 8-bit portion last (rightmost). It is important to note that this is the reverse order to the usual dotted-decimal convention for writing IPv4 addresses in textual form.
For example, an address (A) record for mail.example.com points to the IP address 192.0.2.5. In pointer records of the reverse database, this IP address is stored as the domain name 5.2.0.192.in-addr.arpa pointing back to its designated host name mail.example.com. This allows it to pass the Forward Confirmed reverse DNS process.
Read more about this topic: Reverse DNS Lookup
Famous quotes containing the words reverse and/or resolution:
“They shall beat their swords into plowshares, and their spears into pruninghooks: nation shall not lift up sword against nation, neither shall they learn war any more.”
—Bible: Hebrew Isaiah, 2:4.
The words reappear in Micah 4:3, and the reverse injunction is made in Joel 3:10 (”Beat your plowshares into swords ...”)
“A great many will find fault in the resolution that the negro shall be free and equal, because our equal not every human being can be; but free every human being has a right to be. He can only be equal in his rights.”
—Mrs. Chalkstone, U.S. suffragist. As quoted in History of Woman Suffrage, vol. 2, ch. 16, by Elizabeth Cady Stanton, Susan B. Anthony, and Matilda Joslyn Gage (1882)