Class A IP A group of IP addresses where the first number
remains the same, and the last three can vary. It could be
represented by w.x.y.z, where the x, y, and z can be any number
from 0-255, and the w represents the first static part of the IP
address (e.g., 10.x.y.z). Thus, the number of possible
combinations within the Class A address are 256*256*256 =
16,777,216. Of course, some of the addresses, like those ending
in .0 and .255, are not used, so the actual number of usable
addresses in a Class A is somewhat less than that. The subnet
mask of a class A IP address is 255.0.0.0. Thus, only the last
three digits of the IP address are used to determine where
traffic gets routed within the Class A. There are 254 class A
groups in existence.