TCP/IP Cheat Sheet A Free Study Guide by Boson Software, LLC

The First-Octet Rule: High-Order Bits Determine the Address Class An octet is a binary number of 8 bits, with the lowest possible number being 00000000 and the highest possible number being 11111111, or 28 . The binary number 11111111, or 28 , converts to 255 in decimal format.