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:
“Now listen, buddy, there are a few corny ideas you got to get out of your head if you’re going to fly an airplane. Most things are just the reverse from what people think. The higher you are the safer you are. The Earth down there, that, that’s your enemy because once you hit that, boy, you splatter.”
—Dalton Trumbo (1905–1976)
“I had crossed de line of which I had so long been dreaming. I was free; but dere was no one to welcome me to de land of freedom. I was a stranger in a strange land, and my home after all was down in de old cabin quarter, wid de ole folks, and my brudders and sisters. But to dis solemn resolution I came; I was free, and dey should be free also; I would make a home for dem in de North, and de Lord helping me, I would bring dem all dere.”
—Harriet Tubman (c. 1820–1913)