What is the quickest way to determine your usable IP address in a subnet?

To determine the usable IP addresses in a subnet, understanding the principles of subnetting is essential. The number of usable IP addresses in a subnet can generally be calculated by figuring out the total number of addresses available within that subnet and then subtracting any reserved addresses.

In a standard Class C subnet (with a default subnet mask of 255.255.255.0), the fourth octet can range from 0 to 255. The total number of addresses in a subnet is 256 (from 0 to 255). However, one address is reserved for the network address (the first address) and one for the broadcast address (the last address). As a result, to determine the number of usable addresses, you would subtract 2 from the total count of 256, which gives you 254 usable addresses.

This logic makes "256 minus the 4th octet number" correct, as it aligns with determining the range of available addresses. The calculation directly relates to the basic method used to count valid host addresses within a subnet, giving a clear way to arrive at the numbers needed without confusion. The other choices do not follow the established method of calculating usable IP addresses, as they do not account for the necessary subnetting