Question

A design already includes subnets 192.168.1.0/26, 192.168.1.128/30, and 192.168.1.160/29. Which of the following subnets is the numerically lowest subnet ID that could be added to the design, if you wanted to add a subnet that uses a /28 mask?

Answer 1

192.168.1.64/28

Step-by-step explanation:

Three existing subnets was listed in the question, which together consume part of Class C network 192.168.1.0. Just listing the last octet values, these subnets consume 0–63, 128–131, and 160–167. The new subnet, with a /28 mask, needs 16 consecutive numbers, and the subnet numbers will all be a multiple of 16 in the last octet (0, 16, 32, and so on). Looking at the consumed numbers again, the first opening starts at 64 and runs up through 127, so it has more than enough space for 16 addresses. So the numerically lowest subnet number is 192.168.1.64/28, with range 192.168.1.64– 192.168.1.79.