Final answer:
The highest number an IPv4 octet can reach is 255, as it is represented by 8 bits, with the maximum binary value being 11111111.
Step-by-step explanation:
The highest number an IPv4 octet can be is 255. IPv4 addresses are divided into four octets, and each octet is represented by a decimal number from 0 to 255. Because an octet is made up of 8 bits, and the maximum value you can achieve with 8 bits is 255 (binary 11111111). For example, an IPv4 address might look like 192.168.1.1, where each value between the periods is an octet, and cannot exceed 255.