IP address
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... names because of the desire to unify network number support within
existing IP address to host name support. The existing support is
the IN-ADDR.ARPA ...
... HR].
The new syntax expands the set of names to allow leading digits, so
long as the resulting representations do not conflict with IP
addresses in decimal octet form. For example, 3Com.COM and 3M.COM
are now legal, although 26.0.0.73.COM is not. See [HR] for details.
...
... This mapping is for use in debugging tools and status displays
of various sorts. The conversion from IP address to network
number is well known for class ...
... network
number is well known for class A, B, and C IP addresses, and
involves a simple mask operation. The needs of other classes
...
... The primary application is to be able to identify all of the
subnets involved in a particular IP address. A secondary
requirement is to retrieve address ...
... tree. (A host field
of all zero in an IP address is prohibited because of
confusion related to broadcast addresses ...
... creates
a need to delegate a whole new name space. Since the IP
address space is so closely related to the network number
space, most believe that the overhead ...
... IN-ADDR.ARPA tree that correspond to host-zero IP
addresses. The same method is used for subnets in a nested
...
... Procedure for using an IP address to get network name ...
...
Depending on whether the IP address is class A, B, or C, mask off the
high one, two, or three bytes, respectively. Reverse the octets,
...
...
For example, suppose the IP address is 10.0.0.51.
...
...
Suppose that the IP address is 128.9.2.17.
...
... Procedure for finding all subnets involved with an IP address ...
... RR is found, look up the next level of subnet using the
original IP address and the mask in the A RR. Repeat this procedure
until no A RR ...